What should a person suffering from epilepsy and schizophrenia do, who takes medications that cause them lethargy and sleepiness during prayers and prevent them from fasting Ramadan, and who fears discontinuing them would lead to a return of seizures, and who feels deficient in fulfilling their duties towards Allah Almighty?

You must perform acts of worship such as prayer, fasting, and others to the best of your ability. What you are unable to do, you must make up for when you are able. It is not permissible to delay prayer beyond its time; rather, you should pray it in the manner you are able. Consult a doctor regarding medication. If he informs you that you need it during the day and are unable to fast, then there is no blame upon you.