@julian Thank you for your answer, and yes, that could be where the problem comes from.
I have these plugins on : default composer, alignment, markdown, simple spoiler.
PS. But I don't have the "redactor plugin" if by that you mean a wysiwyg editor.
@Jenkler let's encrypt, and it's easy
Ok, nice. I will try it out for my next projekt
Let's Encrypt - Rulezz!