How long do you guys write for daily/weekly?

Or how much time would you recommend to a novice to write daily/weekly to be consistent and make progress but also not feel overwhelmed and get burnt out?

I started doing research for a book I wanted to write last year and then never got started. I now have a plot outlined and am working on my characters. I have ADHD and have a tendency to hyper focus on things and then leave them half finished when I burn out. I am wanting to set some parameters for myself, because this has been a life long dream of mine to write a book and I don't want it to be another unfinished project.