Would the prayer and good deeds of a Muslim be accepted, despite his committing sins such as talking to girls and seeking out immorality?

The questioner must repent to Allah for speaking with girls and going out with them, and for all that resulted from that, and stop these forbidden acts. What will help him remain steadfast are: avoiding bad company, associating with good friends, becoming attached to the mosque and listening to sermons, and remembering the dire consequences of disobedience. Committing these forbidden acts does not invalidate the prayer or other good deeds, but acceptance is with Allah alone. The questioner should advise his friend who does not pray and explain the seriousness of abandoning prayer; if he insists on not praying, he should not accompany him.