What should I do about my fasting in Ramadan, as a young man on holiday in Europe, knowing that I now suffer from diabetes?

If you intentionally broke your fast in Ramadan (definition), you must repent and seek forgiveness. If the breaking of the fast was not through intercourse, then expiation is not required of you. Similarly, if it was through intercourse, but you had not intended to fast for that day, then expiation is not required. However, if intercourse occurred after the intention to fast, and it was intentional with knowledge of its prohibition, then the major expiation becomes obligatory.

Regarding diabetes: - If your condition allows you to fast, then you must make up the days you missed, and continuous making up is not obligatory. - If you deliberately delayed making up the fast, knowing its prohibition, then you are liable for the expiation for delay. - If your condition is such that there is no hope of you being able to fast, then it suffices for you to give expiation for each day (750 grams of the staple food of your country to the poor).