How to write html

Answer 1

You have started the html course; it teaches you all you need to get started. Try completing it, then ask for specific doubts if any.
https://www.sololearn.com/learn/HTML/1021/

Answer 2

In Internet ( international network) there's many courses and books for Learning HTML5.

Answer 3

Also SoloLearn have HTML course, but it is not full course, after Learning you must found HTML5 courses for professionals