How do I know that Allah Almighty has forgiven my sin, and that He loves me and is pleased with me, especially when I feel His anger towards me due to the difficulty of lowering my gaze in the institute despite my attempts?

It is not possible to be certain of God's forgiveness of a servant and His satisfaction with them. Rather, the servant exists between hope and fear: they hope in their Lord and hold a good opinion of Him, while fearing their sins and shortcomings. They must be mindful of God to the best of their ability, strive against their lower selves to lower their gaze from what is forbidden, and be diligent in obeying God by observing the obligatory acts and performing supererogatory ones, all while holding a good opinion of God and supplicating for the acceptance of repentance and the forgiveness of sins.