What is the path to repentance for a friend remorseful about committing indecency while wearing a condom and the girl taking birth control pills, and should he marry his fiancée before his travel, and what are the supplications and ذکر (forms of remembrance of God) that can help him avoid returning to that act?

This sin is grave, and adultery is a major sin. However, repentance is possible if a person regrets the sin, abandons it, and resolves never to return to it. Whoever repents, Allah accepts their repentance, and they should have a good opinion of their Lord. Marriage is one of the best means to attain chastity, and he should complete it and not dwell on the fact that he fell into what is forbidden, as long as he has repented. Among the supplications that help in maintaining chastity are: "O Allah, I ask You for guidance and piety, and chastity and richness," and "O Allah, grant my soul its piety and purify it, for You are the best of those who purify it; You are its Guardian and Master." It must be noted that residing in lands of disbelief is forbidden for anyone who fears temptation for themselves.