Does assisting someone in cheating on an exam during the daytime in Ramadan invalidate the fast? And are the problems that occurred afterwards a punishment for this sin or a trial? And how can the recurrence of such a situation be avoided in the future?

A person must move beyond past sins after repentance, for the one who repents from sin is like one who has no sin. If a person repents sincerely, then any disagreements or harm that befall him will not harm him; rather, this is good for him, either atoning for previous sins or raising his rank with Allah. Acts of disobedience do not invalidate fasting, but they do diminish its reward.