What is the ruling on masturbation and what is its expiation? Is abstaining from prayer due to ritual impurity (janabah) and inability to perform ghusl considered an act of disbelief (kufr)? And do the medications (Pepon Plus) and (Decongestyl) have an effect in treating prostate congestion?

You must repent to Allah for what you have done, for abandoning prayer is one of the greatest sins. Indeed, some scholars have considered the one who abandons it to have committed major disbelief. Shyness is not an excuse for abandoning ghusl (definition). The majority of scholars hold the view that you must make up the prayers you missed, while some do not. As for your covenant with Allah, it is an oath, and it requires an expiation for an oath, in order, and you must stop the forbidden masturbation.