Hello Kenza,
Thanks for writing in! I have logged in and investigated your issue. I could not replicate any issue though. I was able to edit all three posts that you have mentioned above.

You might be having a browser caching issue. Most probably after you have switched the SSL because you installed Really Simple SSL. I have temporarily deactivated it. You might not even need that plugin. If your SSL certificate is already in your server, you will just have to change the site URL and WordPress address URL in Settings > General from http to https.
I would recommend that you clear your browser cache or use private browsing mode or Incognito mode and test your site again.