Can't update post for 2 days

That’s been 2 days I am trying to update a post (add text and photos) but without much success. Most of the time after hitting “save draft” I get the message “The connection to the server was reset while the page was loading”. When go back I see the version of the post without the latest updates and a message on top “The backup of this post in your browser is different from the version below. Restore the backup” I restore the backup and the cycle repeats. For two days. What’s the solution?