How long does it take to completely finish a lesson
Like from basics to finish how long would it take
It depends on a person's willingness to finish a lesson ( I think your referring to the tree, I don't know, it wasn't informative in your message).
I have heard of people finishing a tree in 3 days, and I have heard of people who have easily tested out of skills with little to no problem. Also, I've heard of people who took almost a year or two to finish a tree, or a week to finish a skill. It really depends on time and commitment.
In average, maybe 1-3 months with good commitment sometimes. Maybe shorter or longer, depends on what you want to put into your time.