Practice, practice, practice. We always know a lot more passively than we do actively and the only way to make passive knowledge active is to put it to use and regularly. This means focusing more on speaking and writing activities.
There are many ways you can go about this. You could write short passages and post them in language learning forums for correction. You could try taking sentences from English-language material and making your own sentences following the same pattern. You could try summarising/paraphrasing content in English, either in speech or writing. You could have a language exchange with someone who is learning your language and work together on idioms, which might be an interesting cultural exchange too, as you learn why certain phrases are used.
It would be impossible to list all the possible ways, but if the activity gets you speaking or writing and you can get feedback from a native/fluent English speaker, then any errors you make will be caught so you know where it doesn't sound natural, and you will either remember them the next time or you won't, but the repetition will result in improvement over time.
Whenever I make corrections on others' work in English, I mark where it's grammatically incorrect in a different way to phrases that sound unnatural. It's grammatically correct to say "I am experiencing extreme happiness that you have requested my presence at your marriage ceremony" but the semantic choices are odd and it takes a few moments to translate that into something more natural, i.e. "I'm delighted that you've invited me to your wedding!"
It is much easier for you to fix your own grammatical mistakes exclusively with the aid of textbooks, but in order to make your language sound more natural in speech or writing, you really need feedback from a native/fluent speaker to set up a feedback loop.