do (one's) level best
To do as well as one can at something. I'm just not good at math, so, believe me, a B- in Algebra means that I've done my level best. No, you're not the star player on the team, but you always do your level best, which encourages the rest of us to do the same.
do your level best
COMMON If you do your level best to do something, you try as hard as you can to do it. The President told American troops that he would do his level best to bring them home soon. They're doing their level best to answer all the questions that people have.
do your level best
do your utmost; make all possible efforts.do/try your level ˈbest (to do something)
try as hard as you can: I’ll do my level best to be there by ten o’clock, but I can’t promise anything.