Thank you for your (name removed by moderator)ut,
“quote"Since when do Muslims dare to speak for God?”/quote"
Your book said that Mohamed did.
“quote"Qur’an as the final and perfect word of The Creator”/quote"
Prove it
Thanks for the opportunity prodigalson,
AND SO we propound these parables unto mankind: but none can grasp their inner most meaning save those who are aware (Qur’an 29:43)
ARE THEN those bent on denying the truth not aware that the heavens and the earth were once one single entity which We then parted asunder? – and [that] We made from water every living thing? Will they not then [begin to] believe? (21:30)
AND IT IS We who have built the universe, and it is We who are steadily expanding it (51:47)
But none will grasp the message except those who use their reason (Quran 2:269)
…there’s so much you deserve to know about Islam

This isnt a Muslim forum though so I dont want to undermine its purpose. But if you care to hear the reason for my intellectual and heart felt conviction in my faith I will do my best. The best thing I think though is to read the Qur’an (for English Speakers – Mohammad Asad’s translation is my highest recommendation, he was an Austrian Jew who dedicated his life to this).
At the end of 30 years of peice by peice revelations, I find it unreasonable to conceive that man can produce a text that, as a whole is consistent to such a degree. Whether it be mathematical, linguistically concise in its grammar and phrasing or its containment of natural truths about life, scientific accounts and historical detail to a level not at all conceivable to anyone 1400 years ago. It is quite fascinating to research (or just to read).
I’ll leave you to it for now, but one pretty fun example of Math is the following: the number of times words are mentioned in the Qur’an regarding significant opposites (keep in mind, these words are scattered throughout the Qur’an, revealed in segments over 30 years and God specifically mentions that they are opposites or equal).
24 - Al Rajul (Man)
24 - Al Mar’a (Woman)
115 - Al Dunia (This Life)
115 - Al Akhirat (The Hereafter)
88 - Al Malaika (The Angels)
88 - Al Shayteen (The Satans)
145 - Life
145 - Death
11 - Iblis (Lucifer – The leader of satans)
11 - Seek refuge from Iblis
Interestingly:
5 - Salat (Prayer) (Muslims pray 5 times a day)
12 - Al-Shahr (Month)
365 - Al-Yawm (Day)
I hope I showed you a pleasant snippet of the the final revelation I have come to love so much

You also asked about the Prophethood of Mohammad (pbuh). I will gladly open this subject up for you after I attend to my personal duties (husband, work, cats etc haha).
My Regards
AND THUS have We bestowed from on high this divine writ as a discourse in the Arabic tongue, and have given therein many facets to all manner of warnings, so that men might remain conscious of Us, or that it give rise to a new awareness in them. Know, then that God is sublimely exalted, the Ultimate Sovereign, the Ultimate Truth: and knowing this, do not approach the Qur’an in haste, ere it has been revealed unto thee in full, but always say: “O my Sustainer, cause me to grow in knowledge!” (Qur’an 20:113-114)