"Turning back" here is an idiom for "changing directions toward." This is the first of two rhetorical questions. AT: "you should not go back to ... principles." or "you should not change back to ... principles." (See: [[rc://en/ta/man/translate/figs-rquestion]])
Paul uses this question to rebuke the people for behaving in a way that would make them like slaves. AT: "It seems that you want to be slaves again." or "You behave as though you wanted to be like slaves again."(See: [[rc://en/ta/man/translate/figs-rquestion]])
Here being "enslaved" is a metaphor for being obligated to obey certain rules or customs. AT: "Do you want to have to obey rules again like a slave has to obey his master?" or "It seems that you want to be controlled all over again!" (See: [[rc://en/ta/man/translate/figs-metaphor]])