What is the ruling on one who swore by Allah to abandon masturbation, then returned to it and sought forgiveness? And what is the ruling on one who cursed the Lord in a moment of anger, then regretted it and sought forgiveness? And is the illness I am suffering from a trial or a result of problems?

Cursing the Lord is a grave act of disbelief (kufr atheem), and anger is not an excuse unless one loses their sanity. Repentance for it is valid. Masturbation is forbidden, and an oath to abandon it must be fulfilled. If the oath is broken, an expiation for the oath is obligatory. Illnesses are trials from Allah by which He tests His servants in times of hardship and ease. It is incumbent upon the servant to be patient with them while taking the necessary means for treatment.