Correct way to add custom hook into header, prestashop 1.7

[prestahench]

So I added this hook with a custom module I made, into header.tpl of Classic theme.

 

this is the code: https://pastebin.com/ynMTb9fh

As you can see I added the hook into the bottom of the code. Everything works on FRONT end however I can see my header at the bottom of some pages in the back office. 

Not only I see my header at the bottom of those pages but it also breaks all the layout and it makes impossible to work on some pages. For example the adding product screen is all bugged.

 

So my 2 questions:

How can I add an IF to tell prestashop to show this module on front end only?

How can I include a custom hook in the header?