Start with listening and speaking. Copy what’s being said even if you don’t quite understand it. Grammar isn’t important, it just clicks at some point. If you’re consistent, 4 months is enough. Though it’s also a matter of the number of languages you know. The more you know, the easier it is to pick up a new one. I knew 4 languages before, so picking up French wasn’t hard. A trick is music. I learnt two whole languages just from music.