Let's talk about why we make grammar mistakes.
It's SO annoying! Especially when the mistakes are easy ones!
1: We have the habit of translating directly from our language
Correct: She is good AT English (English uses 'at' here).
2: We have the habit of saying something logically when English isn't logical
Not correct (but logical): Please call me when you WILL ARRIVE (future tense).
Correct (but strange): Please call me when you ARRIVE (present tense).
3: We haven't been studying at the right level, because the other parts of our English are better than our grammar
This was true for me with Dutch. I was learning Dutch by living in Amsterdam, so my speaking and listening were much better than my grammar. (Crazy, I know!) I fixed this by reviewing Dutch grammar from the beginning.
https://www.oxfordonlineenglish.com/english-level-test/grammar
or this one