How can one make up for 25 days of Ramadan fasting that were not observed for the past two years due to health reasons, now that one's health has improved?

Breaking the fast in Ramadan due to illness is permissible, and one must make up the missed days when able. If the excuse persists, there is no penalty for one who delays making up the days until the next Ramadan. Rather, they must make up the days whenever they are able. They are not required to make up the days consecutively; rather, they can fast some days and break their fast on others, provided they complete the fast before the start of the next Ramadan. No expiation is required for delaying due to an excuse.