"I didn't understand what you say, could you please repeat gain?"

[newkeenlearner]

When in an English class a teacher asks a question that I don't understand for some reasons, what should I say?

Is this OK "I didn't understand what you say, could you please repeat gain?" ?

 

[emsr2d2]

When, in an English class, [STRIKE]a[/STRIKE] the teacher asks a question that I don't understand for some [STRIKE]reasons[/STRIKE] reason, what should I say?

Is this OK? "I didn't understand what you [STRIKE]say[/STRIKE] said. Could you please repeat it?" [STRIKE]gain?"[/STRIKE]

See above.

"Repeat" means "say/do again" so it is tautologous to say "Please repeat it again". You would be asking them to say it again again.