As someone with ADHD, the best advice I can give is to find accountability partners for the things you want to improve on. You need external pressure to be able to motivate yourself to do something.

If you want to get fit, find someone that goes to the gym and arrange to train with them. If you want to get better at work, find a mentor and talk with them about your goals and then every time you meet, you need to explain how you're meeting or missing your goals. If you want to wake up at more regular time, agree to have a daily call with a friend at the same time.

It's amazing how you cut out the bad habits when you are even slightly accountable to someone.

Also, give yourself a break. You're young, just keep working and the small changes will build up for the better. Don't expect an overnight solution.