Answer 1

You can switch courses...
What do you mean by add or delete courses ?

Answer 2

Go to Learn section, click the course name in the top, click Discover Courses.

Answer 3

Click the learn section.
Selected the course name such as html,c++ etc.
Start the learning.

Answer 4

Hi Tamim Moh'd, To add a new course, just head over to the learn section and at the top of the page, click on the name of the course you have started and from there click on the explore new courses button. The button will take you to the collection of sololearn's courses. I think you can also add courses through the community tab.