both

They're both correct, but "remaining" is slightly less colloquial. For instance, if you were working on a project with some coworkers and ran out of time, you would most likely say "we don't have any time left to finish this". If you said "we don't have any time remaining to finish this" it would still be correct, but to some people might sound slightly more robotic. This is highly subjective though, so you can just think of them as interchangeable.

Both are correct.