、。
I studied English hard every day, but didn't learn much.
Literal
Every-day wholeheartedly English [object-を] studied but, not-much stuck-to-body.
一生懸命に ('with all one's might') is a common adverb from the four-character compound 一生懸命. 身につく ('stick to the body' = 'learn, internalize') is idiomatic — its negative 身につかなかった conveys that despite effort, the knowledge didn't take hold. The concessive が sets up the disappointing contrast.