slow and steady pace
Idiomatic expression likening progress to a turtle's slow but steady walk. Often used positively to emphasize perseverance.
His research is slow and steady, but it is making definite progress.
Even if your language improvement is slow and steady, it's important to keep at it.
From the fable of the tortoise and the hare, where the tortoise wins through steady effort. The expression 亀の歩み (turtle's walk) symbolizes slow but persistent progress.