The one I'm familiar with is, bite off more than you can chew, which means to take on something you are unable to handle. For example,
Max: I regret telling Sam that I'd help with the project. It's way too much work!
Pat: Did you bite off more than you can chew?
Max: That and more.
Literally, "to bite off more than one can chew" means, you took a bite out of, say, a sandwich, and the portion of food was so big you were unable to chew it; you could chew some, but not all.
All the best,
- For Teachers