Prostrating to the Prophet (peace and blessings of Allah be upon him) constitutes disbelief in Allah (kufr)
Question

I would like to know what to do. Someone told me that when reciting dhuwa, that i have to prostrate seven times for the prophet[p.b.u.h], but i just don't know how, would you.
Praise be to Allah.Firstly, one of the things that are well known in Islam and that no Muslim has any excuse for not knowing is that it is not permissible to do any kind of act of worship for anyone except Allah – not to any angel who is close to Him or to any Prophet who was sent. Whoever does any kind of act of worship for anyone other than Allah is a mushrik (polytheist, one who associates others with Allah) and a kaafir (disbeliever). The evidence for that is the verse in which Allah says (interpretation of the meaning): 
 
“And the mosques are for Allah (Alone), so invoke not anyone along with Allah”
[al-Jinn 72:18]. 
Ibn Katheer said: Here Allah is commanding His slaves to worship Him alone and not to call on anyone alongside Him, and not to associate anyone with Him. 
This action is a kind of exaggeration about the Messenger of Allah (peace and blessings of Allah be upon him), which the Prophet (peace and blessings of Allah be upon him) warned us against and forbade us to do. He said: “Do not exaggerate about me as the Christians exaggerated about the son of Maryam, for I am no more than His slave, so say, the slave of Allah and His Messenger.” Undoubtedly this action (prostrating) is a form of worship.
(Narrated by al-Bukhaari, Ahaadeeth al-Anbiya’, 3189). 
Undoubtedly this action is a kind of worship, and the Prophet (peace and blessings of Allah be upon him) warned us against following the Jews and Christians in that. He said during his final illness: “May the curse of Allah be upon the Jews and Christians, for they took the graves of their Prophets as places of worship.” He was warning against doing what they did. (Narrated by al-Bukhaari, al-Salaah, 417)
And the Prophet (peace and blessings of Allah be upon him) warned us against standing up for him. It says in the hadeeth [referring to when he led them in prayer sitting down because he was ill, and they were standing, so he gestured to them to sit down]: “Just now you nearly did the action of the Persians and Romans, who stand up for their kings whilst they [the kings] are sitting.” (Narrated by Muslim, al-Salaah, 624) 
And it says in the hadeeth: “Do not do as the Persians do for their leaders.” This is narrated in Saheeh al-Jaami’, 7380. If this is what is said about standing up for him (peace and blessings of Allah be upon him), then what about prostrating for him? 
Prostration in this manner is one of the most exclusive acts of worship, to be done only for Allah, may He be glorified and exalted. Allah has commanded us to prostrate to Him alone and none other, as He says (interpretation of the meaning): 
“Prostrate yourselves not to the sun nor to the moon, but prostrate yourselves to Allah Who created them, if you (really) worship Him”
[Fussilat 41:37] 
“So fall you down in prostration to Allah and worship Him (Alone)”
[al-Najm 53:62]. 
For more information on the issue of prostration to anyone or anything other than Allah, please see the answer to question no. 229780.
Secondly: what is prescribed in Islam is to send blessings upon the Prophet (peace and blessings of Allah be upon him) when making du‘aa’. This is a kind of etiquette to which attention should be paid. 
Al-Nawawi said: The scholars are unanimously agreed that it is mustahabb to begin du’aa’ with praise of Allah, then to send blessings upon the Messenger of Allah (peace and blessings of Allah be upon him), and to conclude the du’aa’ in like manner, as it says in the hadeeth: 
“Whilst the Messenger of Allah (peace and blessings of Allah be upon him) was sitting, a man entered and prayed, then he said, ‘O Allah, forgive me and have mercy on me.’ The Messenger of Allah (peace and blessings of Allah be upon him) said, ‘You are in a hurry, O worshipper. When you have prayed, sit and praise Allah as He deserves to be praised, then send blessings upon me, and then call upon Him (make du‘aa’).’ Then another man prayed and then praised Allah and sent blessings upon the Prophet (peace and blessings of Allah be upon him). The Prophet (peace and blessings of Allah be upon him) said, ‘O worshipper, make du‘aa’, for you will be answered.’” 
(Narrated by al-Tirmidhi, al-Da’waat, 3398; Abu Dawood, 1481; classed as saheeh by al-Albaani in Saheeh Abi Dawood, no. 2756). 
It was narrated that Faddaalah ibn ‘Ubayd said: “The Prophet (peace and blessings of Allah be upon him) heard a man making du‘aa’ during his prayer, but he did not send blessings upon the Prophet (peace and blessings of Allah be upon him). The Prophet (peace and blessings of Allah be upon him) said: ‘This man is in a hurry.’ Then he called him and said to him, or to someone else, ‘When any one of you prays, let him begin by praising Allah, then let him send blessings upon the Prophet (peace and blessings of Allah be upon him), then after that let him make du’aa’ as he wishes.’” Abu ‘Eesa said: this is a saheeh hasan hadeeth. (al-Tirmidhi, 3399; classed as saheeh by al-Albaani in Saheeh Abi Dawood, 2767) 
It was narrated in a hadeeth that ‘Abd-Allah ibn Mas’ood said: “I was praying, and the Prophet (peace and blessings of Allah be upon him) was nearby, and Abu Bakr and ‘Umar were with him. When I sat I started by praising Allah, then I sent blessings upon the Prophet (peace and blessings of Allah be upon him), then I prayed (made du‘aa’) for myself. The Prophet (peace and blessings of Allah be upon him) said, ‘Ask, it will be given to you; ask, it will be given to you.’” (Narrated by al-Tirmidhi, al-Jumu’ah, 541; al-Albaani said in Saheeh al-Tirmidhi, it is hasan saheeh; no. 486). 
If it is asked, how do we send blessings upon the Prophet (peace and blessings of Allah be upon him)? 
The answer is: 
The way to send blessings upon the Prophet (peace and blessings of Allah be upon him) is to say: “Allahumma salli ‘ala Muhammad wa ‘ala aali Muhammad kamaa salayta ‘ala aali Ibraaheem. Wa baarik ‘ala Muhammad wa ‘ala aali Muhammad kama baarakta ‘ala aali Ibraaheem fi’l-‘aalameen innaka hameedun majeed (O Allah, send blessings upon Muhammad and upon the family of Muhammad, as You sent blessings upon the family of Ibraaheem, and bless Muhammad and the family of Muhammad, as You blessed the family of Ibraheem among the nations. Verily You are Most Praiseworthy, Full of Glory).”
(Narrated by al-Bukhaari, Ahaadeeth al-Anbiya’, 3119) 
This is how blessings are sent upon the Prophet (peace and blessings of Allah be upon him). As for what is mentioned in the question about prostrating for the Prophet (peace and blessings of Allah be upon him), this is haraam (forbidden) and is major shirk, because prostration may only be done for Allah. So the Muslim must learn about the matters of his religion from the Qur’aan and Sunnah and from trustworthy scholars; he should ask about everything that he does not understand, so that he will not fall into shirk, Allah forbid.
He should also keep away from everyone who enjoins shirk, bid’ah (innovation) and misguidance. We ask Allah to keep us safe and sound.
And Allah knows best. 
May Allah send blessings upon our Prophet Muhammad.