What should I say if I need to repeat what someone told me to do to be sure I understood?
After listening to instructions, I wannt to know if I understood.what's the phrase?
Let me say it back/
Let me repeat it to you to see if I got it right.

Any others?

Thanks a lot

Question

What should I say if I need to repeat what someone told me to do  to be sure I understood?
After listening to instructions, I wannt to know if I understood.what's the phrase?
Let me say it back/ 
Let me repeat it to you to see if I got it right.

Any others?

Thanks a lot

Answer

Hello!

To make sure you understood correctly, you can also say: 
"I want to see if I understood well: ..." 
”Let me see if I understood this correctly”
”Correct me if I`m wrong" 
"Let me get this straight" 
(Usually, in a conversation, after these phrases, people say what they understood from the other person using different words.)

I hope this helps! :)

Answer

Both would get you there, though the second is better to my ear. If what you have heard is long, you could say (paraphrasing): 'Let me make sure I understand....you want me to...' for example.