I see you don't have any FCs or AAAs yet, so my recommendation would be to start with the very easiest songs at difficulty 1 to focus on the fundamentals and then work your way up. That's what I did when I came back to the game after a 13 year gap and wanted to start getting good at the game. Even though it felt kind of boring (the songs that felt the most fun then were in the 20s and 30s, although I couldn't get great scores on them), and sometimes frustrating (it took me more than 80 tries to get an AAA on Fall into Night, which was only difficulty 2), that's the approach that eventually took me from a completely casual player with zero AAAs to one with more than 1000 AAAs and 2000 FCs.
Have you tried playing around with your gameplay options to find the ones that work best for you? What keys are you using? Most players use a spread approach where the index and middle fingers of each hand are on separate keys on the keyboard, like the A, S, K, and L keys, or the ones I use are A, S, Num5, and Num6 (with the keycap swapped on the 5 so there isn't a pip on it).
Other important options to consider are the scroll speed (faster speeds can mean it's easier to hit notes accurately, but harder to react, most players keep it somewhere between 2 and 3.5), and which game UI visuals to include and how to arrange them. Here's how I set up my gameplay editor as an example, I like to keep it relatively simple but I still find the judge accuracy helpful. Yours doesn't have to look like this but you should think about which visuals are helpful to you and which are distractions.
Ergonomics is also essential, to avoid repetitive stress injuries and also to hit notes better. Develop good habits from the start, and it'll become even more important as you improve towards faster and faster songs. Make sure you have a setup that lets you keep your wrists completely straight, your hands shouldn't be tilted up or down or to either side. And your fingers should be in positions where they can press directly down on the keys, you don't want to be hitting them at an angle or with your fingertips bent. It can help to find something comfortable to rest your forearms on, so your hands stay elevated above the keyboard.
Aside from that, if you want more personalized advice, try saving replays of songs you're struggling with and we can take a look at how to improve them.