He has repented from not praying and fasting; does he have to make up what he missed?
Question

                I was far away from religion and I did not know anything about Islam except that I was born to Muslim parents. I had a relationship with a girl for two years, and after that Allaah blessed me and I became committed. I ask Allaah to make me and you among those who have knowledge and act according to the rulings of Islam. 

Now I am repenting from all my sins by Allaah’s leave, and I have resolved never to go back to them. What I would like to ask you is: I know that one of the conditions of repentance is regret and determination never to go back to the sin, and to restore people’s rights to them if I have wronged them. What should I do with regard to the prayers and fasts that I missed before I became committed? What should I do in order to correct the wrongs I did with that girl, knowing that until now she is not married and she is still not religiously committed?.
Praise be to Allah.
    Firstly: 

    We praise Allaah for having blessed you with guidance, and we 
    ask Him to increase you in knowledge and guidance. We remind you to give 
    thanks to Allaah for this great blessing, for gratefulness increases the 
    blessing. Allaah says (interpretation of the meaning): 

    “And (remember) when your Lord proclaimed: If you give 
    thanks (by accepting Faith and worshipping none but Allaah), I will give you 
    more (of My Blessings); but if you are thankless (i.e. disbelievers), 
    verily, My punishment is indeed severe”

    [Ibraaheem 14:7]

    Secondly: 

    What you have mentioned about the conditions of repentance is 
    correct. With regard to making up missed acts of worship such as prayer and 
    fasting, there are two opinions among the scholars. Some of them say that 
    they must be made up, and this is the view of the majority.  

    Some scholars say that the one who did not pray does not have 
    to make up the prayers that he missed, based on the view that he was a 
    kaafir (when he did not pray). Hence his repentance is his becoming Muslim, 
    which erases all the sins that came before it. 

    Some of the scholars do not think that the one who did not 
    pray deliberately has to make it up, whether they think that he was a kaafir 
    or otherwise, because the text only speaks of those who have excuses, such 
    as the one who sleeps and misses a prayer or forgets it. 

    What is indicated by the saheeh evidence is that the one who 
    does not pray is a kaafir, whether he does not pray because of laziness or 
    denial that prayer is obligatory. See the evidence for that in question no. 
    5208. 

    Obliging the penitent to make up the prayers he has missed 
    makes repentance too difficult, and puts people off. But the penitent should 
    do a lot of good deeds, because Allaah says (interpretation of the 
    meaning): 

    “And verily, I am indeed forgiving to him who repents, 
    believes (in My Oneness, and associates none in worship with Me) and does 
    righteous good deeds, and then remains constant in doing them (till his 
    death)”

    [Ta-Ha 20:82]

    The Standing Committee for Issuing Fatwas was asked: I went 
    to the United States to study and I spent five years there, during which I 
    did not pray or fast. Allaah has guided me and I have become righteous, 
    praise be to Allaah. How can I make up these prayers and fasts? 

    They replied: 

    If the situation is as you describe, and you have repented 
    and begun to follow the way of guidance, you do not have to make up the 
    prayers and fasts that you deliberately did not do, because not praying is 
    major kufr and apostasy from Islam, even if the one who does not pray does 
    not deny that it is obligatory. This is according to the more sound of the 
    two scholarly opinions. If the apostate becomes Muslim again, he is not 
    enjoined to make up the prayers and fasts that he missed during his 
    apostasy, because the Prophet  (peace and blessings of Allaah be upon 
    him) said: “Islam erases that which came before it, and repentance erases 
    that which came before it.”  But in the future you have to pray regularly in 
    congregation and on time with the Muslims in the mosque, and observe the 
    Ramadaan fast. It is also prescribed for you to do a great deal of good 
    deeds and naafil acts of worship such as prayer, fasting, upholding ties of 
    kinship, giving charity and other good deeds, as much as you can, because 
    Allaah says (interpretation of the meaning): 

    “And verily, I am indeed forgiving to him who repents, 
    believes (in My Oneness, and associates none in worship with Me) and does 
    righteous good deeds, and then remains constant in doing them (till his 
    death)”

    [Ta-Ha 20:82

    We ask Allaah to make us and you steadfast in adhering to the 
    truth and following the right path. 

    End quote from Fataawa al-Lajnah al-Daa’imah (6/41). 

    See also question no. 610. 

    Thirdly: 

    With regard to the girl, you should cut off all ties with 
    her, so that the shaytaan will not find a way to tempt you to go back to a 
    relationship with her. If you can find some righteous women who can call her 
    to Islam, that is good. 

    We ask Allaah to increase you in steadfastness. 

    And Allaah knows best.