I got this issue before and I worked it out with Bruno Kos
After quite a while, we could solve the problem and my page went back to normal. Today I enter my backend again and is super slow. My query monitor shows that string translation is again the issue. Obviously I can´t work like that.
Please see attached photo of all the conversation with Bruno to see what has already been done.
I´m in a hurry to fix this since I have a Google Ads campaign running and I really need tohis to stop happening.
Hope to hear from you soon
This needs a detailed debugging, Please share a snapshot of your site so that it is easy for me to check the issue locally without disturbing your site.
You can use the Duplicator plugin to create a snapshot of the site and share the package link with me http://wordpress.org/plugins/duplicator/ your next reply will be private, please share the required details