How do I turn my Passive vocabulary to Active?

Have you tried these tools, plus DeepL that you know already, to check your texts? I haven’t focused myself in the best strategy for improving writing yet but I have intention to do it in few months. Try these for German:

The most important thing is that you collect feedback from your mistakes otherwise you’re not going to improve almost anything forever.

Some of those tools can give you some grammar feedback.

I wouldn’t but I would collect them for grammar categories for the groups that you are trying to learn now. And I’ll keep reading to reinforce those categories step by step so that your mind will pay attention to it and step by step will integrate different aspect of the language.

I’ll wait when advanced to fix the most difficult parts. Imho.

But it’s a work-in-progress for me as well.