Can't delete or type properly in editor

When I try to do css or html exercises, only some of them let me type.I can easily move forward in flexbox for example, but when I do CatApp in html and type in editor it repeats letters and wont let me delete

Are you trying to use it on mobile?

On both tablet and mobile

The site is not well optimised for mobile yet and has plenty of bugs like this.

It’s recommended that you use a computer / laptop with a browser like Chrome.

Edit

If you absolutely need something mobile based, Solo Learn is quite good, and provides tutorials in other languages too, not just HTML, CSS and JavaScript. It’s not quite as robust as freeCodeCamp as far as projects go, but it’ll get you started on learning the syntax you need.