CSS with the header

That text is part of your logo image file

https://jensrosenkrantz.dk/wp-content/uploads/2019/08/logo-6.png

You’ll need to replace the image.

Or, do you meant the text in the tab? See https://i.imgur.com/LtgS5uB.png

To remove that block on every page:

.qodef-title-holder.qodef-standard-type.qodef-title-va-window-top.qodef-has-bg-image.qodef-bg-parallax {
    display: none;
}

To add or override CSS: use the “Additional CSS” option in the customizer. https://codex.ww.wp.xz.cn/CSS#Custom_CSS_in_WordPress

Learn to use the Chrome Developer Tools or Firefox Developer Tools to help you see and test changes to your CSS.