I want to change my son's work schedule
Why do you want to adjust his schedule? Is it for something special?
I want to help my son because he works a lot
It can be hard to watch your child work a lot of hours, but you have no right to change his work schedule. He'll probably get in trouble with his boss if you try. You should leave it up to your son to figure out how much he wants to work.
But I want to spend more time with him. He works too much.
Is there a way you can talk to him about this? He should be responsible for his own schedule. He should be able to find time to spend with you on his own.