out of your element
out of (one's) element
Uncomfortable in a certain situation because it is not the one with which one has experience, familiarity, or expertise (i.e. one's "element"). She usually just orders takeout, so she's really out of her element in the kitchen. I know you're out of your element in this new school, but you'll make friends soon, and things will get better. I asked Alex to consult on this project because I'm out of my element here.