Hi Tia!
Good to see you here! I hope you're doing well. I know you expressed that you feel like you experience symptoms of ADHD, similar to my blog post. It's not easy at all, and I sympathize with that.
In terms of focusing on one project at a time, it depends on your surroundings. Even just now, I was responding to you, and I was in my partners kitchen typing my answer. Him and his mother were speaking to each other, and because of my ADHD, I couldn't concentrate on what I was doing. I decided to go to a quiet space in the house, and then I was able to focus on what I wanted to say to you. If you're not able to do that at home, once you feel more comfortable to be outdoors, try doing this at a quiet cafe or somewhere with internet (but ONLY places that are safe and practising good social distancing and hygiene).
Another thing to note is, if you are already working on ONE project but think of another project and then want to jump ideas, STOP yourself. Instead of jumping from idea to idea, write down your new ideas on a note app or on Google Docs and then when you're finished your FIRST project, start the next one. Go down the list in order (top to bottom), and keep adding as you go, but never skip from one to the other.
Also, turn off your notifications for social media, and if you require music, listen to something like "low-fi chill beats" on Spotify. Those usually have no lyrics and I find them much less distracting (it also helps drown out any background noise or disturbances)
Good luck, and if you have more questions you know where to find me! :) (on Twitter hahah)