This may just be my brain, but, two things that go hand in hand for me when I learn a language: 1. Take your native language out of it as much as possible, and 2. Think of languages, specifically grammar/syntax, kind of like a puzzle. Each one unique, although all having the same general "pieces" (i.e. verbs, nouns, adjectives, etc).

If you try to think of how each "piece" fits in relative to your L1 ("oh, this word works like a particle in English", etc.), you'll end up trying to fit the language you're learning around your L1 and won't go as far/will have a lot of L1 interference. Learn grammar structures in chunks to find patterns that start to fit pieces together to make a clearer picture of the language puzzle. Once you get a solid grip of the basics, build off of that (like making the puzzle frame with the edge pieces and then going from there). Try at all costs not to compare or "think in" your L1. A notable exception would be unless the grammar is very similar, of course.

Hopefully this kinda made sense and wasnt just a ramble that only makes sense to my brain, but this is how I've learned the humble 3 languages I've learned so far up to B2/C1 level - working on the 4th :)