How do i remember stuff faster?

Unfortunatly, I can’t imagine how you must feel, as I’ve never experienced such issues myself yet. However, I did think a lot about it and I think I came up with some decent tips:

Regarding Vocabulary, if you’re able to get the Kanjis in your head, then the vocabs actually are pretty easy (most of the time), as you can pretty easily guess the meaning by just combining the meanings of the Kanjis. For example, if you have 目玉 (eyeball) and you know that 目 means eye and 玉 means ball, you pretty much already know the meaning of the vocab.

As for Kanjis, you should really stick to using the radicals to help you remember them, it makes things a lot easier to break complex structures down into smaller, more familiar pieces.
To remember your radicals and your Kanjis, if the WaniKani mnemonics don’t help you, you have to make your own mnemonics, because that way, you think a lot about that one radical or kanji and how they are built. For example, I recently created just for fun a mnemonic for the for the reading of the cow kanji (牛), which is ぎゅう, the mnemonic goes like this:

Imagine a cow walking past you, and suddenly it starts to sing “Never gonna give you up”. You just got rickrolled by a cow?! Indeed, it is even dancing exactly like Rick himself.
(Hint: Imagine Rick Astely himself with a cow head, singing “Never gonna give you up” and dancing like in the video. Maybe you should also listen to the song to make it stick:

I’m pretty sure you’ll remember mnemonics like this one for the rest of your life, especially if you imagine Rick “Cow” Astley dancing.

Of course, this was just one example for one single kanji, but I think you get what I mean. If that doesn’t work for you as well, I’m pretty much out of ideas.

Hope I could help you!