Hello Dario,
Thanks for writing in!
It seems that Better Wordpress Minify plugin is causing the issue. I have temporarily deactivated the plugin and I was able to edit with the Pro editor. Maybe the plugin is serving the old cache version of the JS and CSS scripts which is why it freezes. Always keep in mind that after doing the updates or site changes, you MUST clear all caches since you have installed BWM plugin so that the code from the latest update or site changes is always in use. This will help you to avoid any potential errors.
Tip: If you are still building your site and pages, please turn OFF any caching and minify plugins. They are best to turn ON when you are done building and ready to go live.
Please check your site now.