He has become Muslim but his mother wants him to go back to being a Christian
Question

                I am an 18 year old student from Greece. About two weeks ago I became a Muslim. I pray normally five times a day, I go to the mosque and I study the Quran. However, I have faced some problems since then. My girlfriend has accepted this and we plan to get married in the future. My sister also accepted the fact. My mother is the problem. She has become very cold with me. She wants me to become a christian again and she cannot accept Islam by no means. She told me that christians will think of me as a traitor and that Muslims will say that I am inferior to them, because I was born christian. I haven't told my father anything yet (my parents are divorced), because he will not accept it (he is christian, too) and he will argue with my mother. My best friend is Muslim and he has helped me a lot, but my mother thinks that he made me become a Muslim, which is not true. I studied Islam and I realized it is the true religion, so I embraced Islam. What do you advise me to do with my parents? I don't want them be disappointed, especially my mother, because she already suffered a lot with the divorce. Thank you for your attention.
Praise be to Allah.
    Firstly: 

    We congratulate you for this blessing that Allaah has 
    bestowed upon you, for by Allaah it is the greatest of blessings and it is 
    guidance by means of which we ask Allaah to admit you to Paradise and join 
    you thereby with the Prophets, siddeeqs, martyrs and righteous. 
    Congratulations to you, for you have turned to Allaah at the same age at 
    which many of the best of the companions of the Prophet  (peace and 
    blessings of Allaah be upon him) turned to Him, such as Mus’ab ibn ‘Umayr, 
    ‘Abd-Allaah ibn Mas’ood, Mu’aadh ibn Jabal and Sa’d ibn Mu’aadh. 
    Congratulations, for the record of your deeds has become white and pure, 
    uncontaminated with sin. Islam erases that which came before it, so now you 
    are starting a new life, a happy life in sha Allaah. We ask Allaah to 
    protect you, make your heart steadfast and guide your parents, siblings and 
    loved ones. 

    Secondly: 

    We praise Allaah that you have started the path of guidance 
    by going to the mosque and studying the Qur’aan, for this is a good sign. 
    The Prophet  (peace and blessings of Allaah be upon him) said: “When 
    Allaah wills good for a person, He grants him understanding of Islam.” 
    Narrated by al-Bukhaari, 71; Muslim, 1037. You should do your utmost to 
    memorize Qur'aan and recite it, pray at night (qiyaam), learn its rulings 
    and act upon it, because in Paradise there are different degrees and levels, 
    and it will be said to the companion of the Qur’aan in Paradise: “Recite and 
    rise (in degree), for your status will be commensurate with the last verse 
    you recite.” 

    Thirdly: 

    The attitude that your mother is expressing towards you comes 
    as no surprise. Your real battle is with the shaytaan, who is not pleased 
    that you have become Muslim, and he does not wish you well. Undoubtedly he 
    will make use of your relatives and whisper to your family, so that he can 
    use them as a weapon against you and prevent them from joining you in the 
    true faith. Do not grieve or despair; seek refuge with Allaah from the 
    accursed shaytaan so that his plot against you may be foiled. Be kind and 
    compassionate towards your mother, for if she tasted the sweetness of 
    guidance, she would not stand in your way. Seek the help of Allaah in 
    calling her to Islam, be sincere towards her and make a great deal of du’aa’ 
    for her, asking for guidance and mercy for her. Perhaps your du’aa’ will 
    coincide with a time when prayers are answered, and you will have the joy of 
    seeing her become Muslim. 

    Remember that you are not alone in this matter. There are 
    thousands of people whom Allaah has guided to the truth and who have chosen 
    Islam willingly, out of conviction. Many of them have met with opposition 
    and resistance from their families, then Allaah willed that their hearts 
    should be opened, and the entire family has become Muslim. That will weigh 
    in the balance of the son who was first guided. We ask Allaah to make you 
    one of them and to grant you the joy of seeing your whole family become 
    Muslim. 

    Remember that opposition from family members is a test for 
    the Muslim, so that the sincerity of his Islam and the strength of his faith 
    may be made manifest. Allaah says (interpretation of the meaning): 

    “Alif‑Laam‑Meem.

    [These letters are one of the miracles of the Qur’aan, and 
    none but Allaah (Alone) knows their meanings.]

    2. Do people think that they will be left alone because 
    they say: “We believe,” and will not be tested.

    3. And We indeed tested those who were before them. And 
    Allaah will certainly make (it) known (the truth of) those who are true, and 
    will certainly make (it) known (the falsehood of) those who are liars, 
    (although Allaah knows all that before putting them to test)”

    [al-‘Ankaboot 29:1-3]

    Among these examples of righteous believers is the great 
    Sahaabi Sa’d ibn Abi Waqqaas (may Allaah be pleased with him) who used to 
    honour his mother. When he became Muslim, his mother refused to eat or drink 
    until he recanted his faith, but he refused to do so and remained steadfast 
    in Islam. His mother found no benefit in her “hunger strike” so she went 
    back to eating and drinking. It is narrated that he (may Allaah be pleased 
    with him) said: “O mother, you know by Allaah that if you had one hundred 
    souls and each soul departed one by one, I would not give up this religion 
    of mine for anything. If you wish, then eat, and if you wish, then do not 
    eat.” So she ate. 

    See: Tafseer Ibn Katheer, 3/429 

    Fourthly: 
The Qur’aan also deals 
    with this problem, because it happened a great deal, especially in the first 
    generation that left kufr behind and embraced Islam, and experienced intense 
    hostility from their family, tribe and the closest of people to them. Allaah 
    says (interpretation of the meaning): 
“And We have enjoined on 
    man (to be dutiful and good) to his parents. His mother bore him in weakness 
    and hardship upon weakness and hardship, and his weaning is in two years - 
    give thanks to Me and to your parents. Unto Me is the final destination.

    15. But if they (both) strive with you to make you join in 
    worship with Me others that of which you have no knowledge, then obey them 
    not; but behave with them in the world kindly, and follow the path of him 
    who turns to Me in repentance and in obedience. Then to Me will be your 
    return, and I shall tell you what you used to do”

    [Luqmaan 31:14-15]

    There is no room for obeying parents in kufr, or for obeying 
    them in sin, but this does not mean that one should not treat them with 
    kindness and respect, and take care of them, and do one’s utmost to guide 
    them. This is indicative of the greatness of Islam, for it is the religion 
    of compassion and love. Hence it calls upon its followers to guide people 
    and bring them into the blessing into which they have entered. 

    Fifthly: 

    The one who has chosen the path of guidance should not pay 
    any attention to what other people say and he should not be surprised by it, 
    because that is something to be expected. What else will the Christians say 
    about you? Will they say, “You have been guided and found the truth and you 
    show it preference over your family and relatives”? No, they will never say 
    that! So do not pay any attention to what they say, whether they call you a 
    traitor or anything else. Regard them with compassion and strive to guide 
    them, and strive to learn so that you can become a daa’iyah who can save 
    them from their misguidance and deviation. 

    With regard to your mother’s saying that you are inferior 
    because you were born Christian, this is not true. Rather we say that you 
    are our brother; you have chosen guidance and have returned to the fitrah 
    (natural state of man) in which you were born. You were born a Muslim and a 
    believer in Tawheed. The Christian scholars know that the child is born in a 
    state of fitrah, hence they hasten to baptize the infant, believing that if 
    he is not baptized he will become a Muslim! This indicates that the basic 
    nature of man is Islam, and that if the child were left as he is he would be 
    a Muslim.  

    In Islam, no one is inferior to anyone else, except to 
    Muhammad  (peace and blessings of Allaah be upon him), because the 
    Prophet is the Messenger whom we are commanded to follow. Apart from that, 
    Islam teaches its followers to be free from the domination of priests, 
    rabbis and monks, and states that a person has no need for any intermediary 
    between him and Allaah. 

    Finally, you say in your question that your girlfriend has 
    accepted that you are Muslim and that you are planning to get married in the 
    future. Here it should be noted that because Islam is keen for its followers 
    to be chaste and for their hearts to be pure, it forbids men to have 
    girlfriends. Islam does not approve of any such relationship between a man 
    and a woman unless it be within the framework of marriage. If your 
    girlfriend is a Christian, then you have to call her to Islam and strive to 
    guide her. This will bring a great deal of good for both of you, in sha 
    Allaah. If she refuses then tell her that Islam forbids this relationship 
    between you and that you can never put pleasing anyone, no matter who he or 
    she is, before pleasing the Most Merciful. You should either get married 
    (and it is permissible for a Muslim man to marry a Christian woman) or 
    separate, preferring to seek the pleasure of Allaah, may He be glorified and 
    exalted. 

    The most important advice we can give you is to treat your 
    mother and father, siblings and relatives, kindly and understand their 
    feelings. Ask Allaah to guide them, and choose wise methods of calling them 
    to Islam, such as kind words, gifts, visits, inviting them to visit the 
    mosque, and giving them useful booklets and tapes. 

    We ask Allaah to take care of you and to help you to do all 
    that is good. 

    And Allaah knows best.