How to Edit Header in Wordpress Themes

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I created my site using the Experon theme which is great! However I’m trying to figure out how to edit the links on the right hand side of the header. I only want links that I populate, not ones that auto generate when I create a new page in WP. Thank you for any assistance.
How to Customize Your WordPress Website Header
Although this element is a standard module which can be found on every site, features of a WordPress header solely depend on a theme you’re using. While most of the free and premium themes will let you handle images and videos that you can adjust in details, some won’t let you customize the header at all. Hopefully, you’ve selected a good WordPress theme from the first group, and now you’re interested in how to customize your WordPress website header. If not, you’ll have to edit theme files. There’s no way around it.
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I need to add code before the DOCTYPE tag, so where can I find your code that writes in the DOCTYPE tag? Or if that is bound in JavaScript, which file can I edit to add my PHP so that it appears before the DOCTYPE tag in all pages?
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Thank you for your patience. Now I got back the text. I activated another theme, and then back to Dream-way. I didn’t do anything else, so I don’t know how the text disappeared and appeared again. Bot sorry, I don’t understand the instructions on the links. I should like to put a little logo instead of the title Betta Szépségszalon. Or beside it, I don’t know yet, I will try. How can I see the <h1>Betta Szépségszalon</h1> in the html? Is it impossible?