What should I do after I master HTML,CSS,Javascript...

Answer 1

www.sololearn.com/faq -> #1 query under web development.

Answer 2

Jquery, angular Js , Node Js, Sql linking

Answer 3

Learn all the different web frameworks, learn PHP (JS is front-end,probably do back-end too)

Answer 4

Go for Angular js, Node js, React js and also learn ionic which will help you to develop hybrid mobile app