Recently I read something like "If God is All Loving and God definitely has the power why doesn't he simply make everything good and stop all this suffering". Also I am pretty sure that I heard that "God doesn't want to send people to hell so why doesn't he send everyone to heaven instead of punishing". As Muslims we shouldn't mess with what God tells us to do and God knows what we know not but for a Non Muslim stuff like this can be the decision between religion and not and statements like these often make someone disbelieve in God. (If there is any) What are the Islamic teachings on why people suffer and why doesn't God send everyone to heaven and why doesn't God make everyone Muslim and good so they can be rewarded? What is a suitable answer that we can use if a Non Muslim says this?
Why people suffer is directly addressed in the Qur'an: it's part of being tested prior to the afterlife.
And We will surely test you with something of fear and hunger and a loss of wealth and lives and fruits, but give good tidings to the patient, Who, when disaster strikes them, say, "Indeed we belong to Allah, and indeed to Him we will return." Those are the ones upon whom are blessings from their Lord and mercy. And it is those who are the [rightly] guided.
Suffering is also sometimes brought on by sin, and this is mentioned in the Qur'an, e.g.:
And whatever strikes you of disaster - it is for what your hands have earned; but He pardons much.
(See also Qur'an 30:41.)
Why mankind was created is explained directly in the Qur'an:
And I did not create the jinn and mankind except to worship Me.
Unlike humans and jinn, angels cannot choose to disobey Allah (Qur'an 66:6, 21:27, and 21:20). So indeed Allah created a being incapable of evil. However, this implies that angels don't have free will, or at least have their freedom limited (Are angels free-willed, perfectly ethical beings?).