Here are some common phrases to use when you don't understand what someone says to you:

Could you say that again, please?
Can you say it a little more slowly, please?
I'm sorry, I didn't understand that.
Sorry?
What does X mean?
What's the meaning of X?

Here are some phrases you can use when you need help with your English:

How do you say X?
What's the English for X?
How do you spell it?
How do you pronounce that?

You can find more useful classroom language here: classroom_language.pdf

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