What are the consequences of intentionally breaking the fast in Ramadan on an unknown number of days, and is it sufficient to fast for 60 days and offer sincere repentance?

You have committed a great sin by intentionally breaking your fast during the day in Ramadan. You must make up for the days you missed, but expiation (kaffarah) is not required except for breaking the fast through intercourse. If you do not know the number of days you missed, then strive to determine them and make up what will give you certainty or a strong presumption that you have fulfilled your obligation. You are also required to perform sincere and true repentance and feel remorse for this great sin.