out of your depth
US /aʊt əv jʊər dɛpθ/
UK /aʊt əv jʊər dɛpθ/
1.
in a situation that is too difficult for you to understand or deal with
:
•
I felt completely out of my depth in the advanced physics class.
•
He's a good manager, but he's out of his depth when it comes to international finance.