What should I do if I have a wet dream while fasting in Ramadan, or if semen is discharged due to doing something I know arouses me? And is ghusl (ritual bath) immediately obligatory in both cases?

A wet dream during the daytime in Ramadan does not affect the validity of the fast, and one must perform ghusl (ritual bath) if the time for prayer enters. If semen is emitted due to one's own actions (such as masturbation, kissing, or foreplay), then one's fast is invalidated and requires a makeup day. As for the emission of semen due to repeated looking, it invalidates the fast according to some scholars. However, if the emission of semen is due to mere thought, it does not invalidate the fast. Ghusl is obligatory in all these cases once the time for prayer enters.