Make the button “BUY THIS COURSE” redirect to profile

Hello,
Courses are paid for outside the website, and i assign the usernames and access to the courses.
I changed the “Buy this course” button to Sign up for this course. if the user has the course allocated to his account he immediately has access otherwise he’s redirected to checkout.
I want that button to redirect to profile instead if the user is logged out, if he’s logged in and doesn’t have the course allocated i want to redirect him to a contact page.
could you please help me, i don’t know where to start. or where the code i need to change is located
Thank youu.