You need to learn how to use them so gramma, use patterns and as somebody else mention here there non kanji words. Knowing words make learning those easier. Japanese is very different grammatically then English (and most languages) and very simplistic making it actually more difficult to understand, so it require practice to get use to, Kanji alone won’t help you out here. I can recommand nihongo no mori beginner grammar course (it actually fun series to watch), google “JLPT gramma” which usally leads list of diffrent gramma patterns and just read japanese, read sentences examples in tatoeba or jisho and ofcrose reading raw manga niconico seiga (hit マンガ tab) got lot of free stuff to read including all free web comics.
Hearing (and inherently talking) requires different kind of practice, because your brain need to analyze sentences way faster then you do during reading and you don’t have Kanji (and as result visual memory) to help you out. Most straight forward method for that is use Japanese in practice… so talk to actual Japanese people, or at least listen to them for starters. If you want to talk to random Japanese people i personally recommend VRChat (you don’t need VR to play it) and go to world “Fantasy Sekai Jou” (it written like that), “[JP] Tutorial World” or “Poppy Street” where they sit a lot.