I use github to code html sites and to host it but I do not find a way to see the errors of my site on mobile.
Is a way to see the errors of a site on chrome or samsung browser on android mobile or does anyone know a site where you can see the errors of another site (not only of the html file for all imported files) ?
You can use each browser's developer mode to show the mobile version of a website. Check out the documentations e.g. for Chrome, Firefox and Safari.
You can use mobile device farms to remotely connect to a smartphone and control it. There are paid services for this like browserstack. Samsung also offers remote connections to its devices for free in their remote test lab.
You can install an android emulator and download various browsers. The easiest approach is to download and install Android Studio and set up the emulator there. For iOS you require a Mac and Xcode.
You can use tools like Google's Lighthouse to check your website for errors. Additionally, if you set up Google Search Console for your website, you'll get automatic reports if your site contains obvious problems. It can find problems on mobile websites when the text is too small or if buttons are too close together.