You need very little grammar in the first place. And if you learned your native one, it becomes easier to just store the difference (leaks may still happen). Coherent input where previous words are repeated while you learned new one are best (watch subtitled movies, and you can pick a lot if you’re focused on that).
Probably especially with a related language. I remember high school French (vaguely) abd it was probably a pretty good 4 years of high school French. But I also remember memorizing a ton of complex tenses and the like, many of which I probably rarely use in English, couldn't name, and would probably be hard for a lot of people to parse if I did, especially conversationally and mixed with negation.
Yep, French has a lot of rules! But they are grammar rules only. So while rote memorization is hard, a good tutor can hel you with the basic understanding. At the end of the day, it’s just practice. With english, you have to practice spelling and pronunciation, with French you have to practice grammar.
