Sadly I can’t give any recommendations for French :( hope someone in this thread who is learning French can pitch in. If not, then it could be a good idea to make a post in this community asking for one maybe?

I know exactly how you feel though. I started my German language learning with duolingo (still do it!) and while it’s fun I felt like I started struggling later on at higher levels since I didn’t really understand the sentence structure and certain rules. Got myself a grammar book and I started enjoying duolingo again after that and find it still really useful for actual vocabulary training.