html code don't can insert

Hello,
whenever I paste an html code in the editor (change to edit code), it changes to entities. It is a bug? Or how can insert a html-code?
Sorry, but i can upload a screenshot here. If i click button insert image comes this "". I use the actual browser brave.

I insert in:

<p><</p>
<p>!</p>
<p>-</p>
<p>-</p>

It should be this: <!--

sincerely

Torte