Getting blank page on any action in admin

I’m getting a blank page if I do anyting in admin area. Such ash posting a post, page, saving settings, disabling addons etc. Cant do anything, after clicking on something that should save something it leads to a blank page.
Even my ajax event calendar is blank.
Tried to disable all my addons, but it doesn’t helped.

Please, do you have any idea? Even if you need any more information just post it please. It is very important for me.

Thank you for your help!