Can’t change website’s title

Hey guys!

I hope this is the correct forum to place my question.

I’m setting up a blog using the theme “flat”.
Today I wanted to change the name that’s displayed in the browser’s tab from the url to an actual name. But for some reason nothing works.

I tried placing <title> my websites name </title> at the very top of my header.php document. I tried using the option via settings>general of WP. I tried different forms of the <title> command that I copied from various forum threads I found online. I tried putting a command that involved…filters? into the functions.php.

Nothings works and I have no clue why. I feel like the template is maybe messing with the manually inserted code or something?

Pleaaase help me.

(English is not my native language. I can totally understand everything written but my written English is not perfect)