You can improve to some extent with patience and effort! For Adhd, stimulant medication is first line of treatment and i suppose you’re already taking medication, but if not i would propose you look into it as it will assist you. Perhaps it can have the effect of sufficiently ordering your thoughts as you speak, improving your intelligibility. You can also improve confidence with frequent practice and getting feedback / positive reinforcement. For practice I recommend a speaking club like the daily online English meetup for 1:1 conversation practice https://meetup.com/daily-english — it’s for both English learners at high levels and people working on their communication alike.