expression, godan verb (-su)
get over the hump; get through the hardest part
Idiomatic expression for passing the most difficult or critical stage of a task or project, after which things become easier.
このプロジェクトも一山越したから、あとは楽になるだろう。
We've gotten over the hump with this project, so the rest should be easier.
試験勉強は一山
I've gotten through the bulk of exam prep, but there's still review left.