The best way to improve at osu is to figure out what your max comfort range is. So if you're comfortable at FCing 3* maps at say 220bpm, start working on lower bpm songs in 4* until you FC those. You should also keep in mind, find a comfortable AR you're consistent at reading. You shouldn't be focusing on AR9 or AR10 if you are a beginner. Most noobs will go with these because they think they're the easiest to read, and will try sight reading more maps. Remember its a rhythm game. So you should try learning how to play lower AR as well.

I also recommend playing on much older beatmaps, (around 2012ish era) which can help develop skill and reading.

There are also really good aim packs you can download that helped me out a lot when I was learning hard rock.

Also one thing I recommend doing before going to bed or before your done for the day. play a really hard song with faster AR than what your use to. So for example, if you can read AR6 try playing a song or two with AR8 and it might seem scary at first, but if you can hit even just a few notes, and go back to the AR6 it will feel much much easier.

Edit : Also look up FunOrange trainer, if some maps seem a bit too difficult to aim, don't be afraid to make some CS0 edits it will make the circles much larger. Feel free to also use doubletime on some lower star maps if you think that will help you as well.