Is man predestined or has free will, and to what extent does this free will apply to matters such as marriage and good deeds?

It is incorrect to say that a human being is either completely predestined or completely free-willed. Rather, they are both predestined and free-willed at the same time. They are free-willed because Allah has granted them intellect, perception, and will, enabling them to distinguish between matters and choose for themselves. For this reason, religious obligations are attached to them, and they are deserving of reward and punishment. And they are predestined because all their actions do not fall outside Allah's power and will, for "everyone is facilitated towards what they were created for."