I would like to start by saying that I'm going to be addressing your concern with understanding speech, and nothing about kanji, because I only have a basic understanding of kanji lol. :)
I've been learning for about a year, and I've found many apps, though I've only used a few. And I have only joined Renshuu recently, so I don't know a whole lot about it. I started on Duolingo, which gave me the foundation I needed, but I think Renshuu works just as well for your purposes.
I also read a well-known grammar book in the Japanese learner community, which is called Tae Kim's Guide to Japanese Grammar. You can download the PDF if you just search for it on Google. It really clarified a lot of grammar concepts, and has lots of info about conjugation. It was definitely confusing at first, but began to make more sense as I got used to the language.
I tell this to anyone looking for advice, but the most helpful thing in my journey so far has been to watch and listen to Japanese content. A lot of it. Examples include movies, videos, podcasts, interviews, skits, whatever you like!
It is extremely difficult, but what really helps to improve is to watch without English subs. I actually prefer Japanese subs because I'm lwk kind of deaf and it also helps to practice reading at the same time. Without the English subtitles, it's magnitudes harder, but it is so worth it. My brain was able to pick up on common anime phrases and their meaning without ever learning them, with ease! And you can also solidify words and grammar into your memory really really well with this.
Sometimes I'll recognize a word but forget it's meaning, so I'll look it up really quickly, and that really helps with retention. I have an app I got on the Google play store that's called Takoboto, which is a Japanese dictionary, and it's more accurate and reliable than Google Translate if you need to look up a word.
Anki can get you some really good study decks, if you know what to look for. There's a particular one called something like Beginner Japanese Using Tae Kim's Guide and Anime or something. It sounds cringe but it's actually really helpful. It explains everything that's in the Guide, along with examples from anime using real voices (and not AI, which is really nice), which definitely helps to remember stuff, and I've learned a lot from using it.
I really must warn you, though, that in anime they use words and phrases that are unheard of in real life. So I just recommend to do some kind of research in what words are anime-y and rude, and on how to be polite. You can actually find skits and informative shorts or videos on YouTube that tell you these things. I actually like those since they're usually funny, too!
Whatever you decide to do, I believe that with enough courage and ambition, you can achieve anything! It might not look like you're progressing, especially in the early stages, but trust me, as long as you continue to learn, you will constantly improve, and someday, you'll look back and wonder how you even got there! Good luck! (◠‿・)🤞
