Podcasts in your target language.

Apps aren't the best for grammar. Duolingo used to have a little discussion forum for each question which was really nice because you could ask why you got it wrong and native speakers would post in-depth explanations, but they got rid of that years ago.

YouTube would probably be a better place to find good in depth explanations about grammar, and you'd be able to comment to ask the teacher questions.

I tried duo lingo and I like it for vocabulary but I need more direct instruction for grammar. When it got more complicated I kept feeling lost. Any favorite apps?