What does Islam say about suffering?
Yes, anyone who is not Muslim and passed the age of puberty will go to hell forever if they die before they become Muslim.
and if a Muslim do bad stuff which is mentioned in the Quran, they also go to hell for a period of time
but anyone who says Lailaha Ilala Muhammadura Sulalah (FROM HEART) will go to Heaven after they are punished.
In Islam anyone who kills someone for no reason will go to Hell Infinity just like non Muslims.
in Islam, suffering during one's lifetime is a way to cleanse the self of shortcomings and sins. However suffering should not be self inflicted or inflicted on others and the ability to indure the period of suffering and being patient will be rewarded greatly as god promised in the quran.
Islam does not specify if non-Muslims go to hell or not. It only confirms that non-believers will be punished but states that those who believe in god but are not Muslims will be judged by god and only he can decide their fate and no body else has the authority to do so. In the quran non-Muslim believers are called "people of the book" and Muslims are instructed not to interfere with their ways of worship and that their churches and synagouges are not to be touched in any way or converted to mosques.