As-salaamu aleikum bro,
This is a deep theological issue and debate. We read in the Qur'an:
"Indeed God does not forgive the ascribing of partners to Him, but He forgives anything else, to whom He pleases, and whoever ascribes partners to God, he devises a great sin. (Qur'an 4:48 )
God will forgive anything else, if He so wills, but the sin of ascribing partners to God is punished in Hell with certainty.
If ye reject (God), Truly God hath no need of you; but He liketh not ingratitude from His servants: if ye are grateful, He is pleased with you. No bearer of burdens can bear the burden of another. In the end, to your Lord is your Return, when He will tell you the truth of all that ye did (in this life). For He knoweth well all that is in (men's) hearts. (Qur'an 39:7)
Whether punishment in Hell is eternal for disbelievers is a complex matter though. If you're interested I can forward some links.
Salam