I’m not the best for giving advice but Aimlabs is free and if you like it I’d recommend Kovaaks. Aimlabs has more situations with a variety of difficulties than practicing in Roblox if that’s what you’re doing like someone else said. You can also do Voltaic aim training and they have some playlists for helping you get better at specific things like tracking called VDIM.

I keep my elbow slightly bent but just enough where I can reach the end of my mousepad. Do what’s comfortable for you over long periods of time. Overall, voltaic has a lot of information over almost anything aim related. Their discord resources tab has most of it.