What is incumbent upon one who owes four Ramadans due to a chronic illness that prevented him from fasting them, and now he is able to fast Ramadan with difficulty? And how is the feeding done, and what is its measure?

Whoever breaks their fast due to an illness that is expected to pass, must make up for those days, as Allah the Almighty says: {And whoever is ill or on a journey - then an equal number of other days.} (Al-Baqarah: 185). However, if the illness is chronic and not expected to pass, then they must feed a poor person for each day, as Allah the Almighty says: {And upon those who are able to [fast, but with difficulty] - a ransom [as substitute] of feeding a poor person.} (Al-Baqarah: 184). If you are able to make up for the fasts, even if it means delaying them, then making them up is obligatory upon you. Otherwise, you should move to feeding for each day a mudd of food (approximately 750 grams).