Observation Details
HTML heading <h1> is used for "MagentaSport: Alle Angebote im Überblick" which implies all heading level two being "Angebote". While the main heading accurately describes the "Angebote" section with the possibility to learn more about the tariffs, it does not describe following <h2> headings.
As heading structure is the most crucial way to navigate a page for many users of assistive technology, each heading must accurately describe topic / purpose of the content it introduces.
What is used as the page's main heading is a construct of an image and a generic container with textual content being "Magenta Sport. Live-Sport überall streamen". This content however does not use a semantic HTML heading element.
Remediation Notes
Ensure correct heading structure. Each heading must accurately describe topic / purpose of the content it introduces / groups. This means, the main heading <h1> must describe the whole page content.
As the main heading content already exists in form of "Magenta Sport. Live-Sport überall streamen", the current <h1> could be made into an <h2>. The main heading then can be made:
<h1>Magenta Sport. Live-Sport überall streamen</h1>Or, if the image version of the "Magenta Sport" text is crucial:
<h1>
<img src="..." alt="Magenta Sport" />
Live-Sport überall streamen
</h1>