Set clear, achievable goals. Use AI. Today it's absolutely foolish not to. If this is your second language, get a coach or teacher. If this is your third, fourth, etc... well, you probably already know the drill, so just make the best use of the tools out there.

Listen to it read it first you understand then you speak plus talk with others specially natives both speaking and writing the language that's exactly what you did when you were young think about it that's how language acquisition works we're not special we've just born in a place and listened to the same language all day everyday till we started to catch up and challenge ourselves with conversations plus we've wrote and read specially in school and now on social media just do the same...

There are only two ways to do this one is immersion by watching tv shows and films in the target language and read and write in the language social media helps a lot but you'd still miss native people to talk and better your speech or you can move to the country and do it altogether!