How to get better?

Hey,
im playing Stepmania for 3 Month´s now.
It feels like im at a point where i won't get any better, my brain just can't think fast enough at these 14/15 difficulty Songs.
Here are my best gameplay´s




Do you have any advice on how i could get better?

practice

Are there any specific training songs or do you have any other advice on how to practice?

Try to play roughly the same amounts of everything for a while, and then if you notice that you're lacking in one or two areas(for example jacks) then bump it up to about 80% those things and 20% problematic things until you're good.

You may think that going all out with stuff you struggle with is a good idea, but trust me, that's how most osu scrubs get bad at high density - they focus on higher and higher Approach Rates which with easier stuff means mostly low density until they get at the point where there's harder stuff with more density but ARs don't go up anymore and they're boned.

A tip I could give is having key bindings close to each other. For example, my key binds are...
Up = T
Down = G
Left = F
Right = H/Y

Left middle finger is on F, left index finger is on G
Right middle finger is on Y, Right index finger is on T

Since the keys are right next to each other, it helps whenever there are crossovers or long streams. It can keep a nice flow of motion.

Search on google some song packs and after a few months on said songs, change the difficulty. thats what i do.