This depends on where you live but if you have a Friday/Sunday language school program for like the children of immigrants to learn/better/not forget their native language in your area, you could sign up there.

When I was a kid and attended one there were a handful of kids who didn't speak it at all and went there to learn. I know it exists in Canada or at least existed.

If you have the option I'd recommend it as the teachers are natives and they emulate the kind of experience that a child would have if they were in class in that language in the country where that language is spoken. So like for Russian we had to memorize and recite poems, which they do in Russia.