Basic phrases to interact with others

Please...
Sorry...
Hey...

I don't understand...
I do not understand...

I didn't understand...
I did not understand...

Wait...
- a minute.
- a second.
- a moment.

Can you repeat?
Repeat the last part...
Repeat all...

Can you explain again?
Explain the last part...
Explain all...

I have a question...
I have a doubt...

I have to go...

Homework!

How do I say (...) in English?

What does (...) mean?
What is (...)?