What is fate, what things change it, does supplication change fate, and is the destiny related to choosing a wife connected to fate, and can it be changed or is it written by God and cannot be changed?

Qadar (Divine Decree) is what Allah has ordained and decreed concerning the events that occur. Nothing happens in the universe except that Allah has known it and willed it. Qadar is of two types: an unalterable decree (qada' mubram) that does not change, and a suspended decree (qada' mu'allaq) that can change through certain actions, such as supplication (du'a), maintaining ties of kinship, and honoring one's parents. Supplication is the most powerful means of averting (or altering) Qadar. The choice of a wife falls under Qadar, but Islamic law requires a person to take the necessary means to choose a righteous wife.