Can’t update website

Hi all,

I just can’t make any update to my website so far. I am using the VPBakery Page Builder plugin and for a reason I can’t explain, any change is not possible.

Every time I try to update an image or a text bloc, the bloc does not load and all I can see is this:

https://www.dday-overlord.com/img/Capture.JPG

I have removed all the different plugins and tried with all of them separately, nothing helps.
I also tried to work on my widgets, I can’t Save them. Everytime I try to modify one, the “Save” button keeps loading, but nothing is saved in the end.

Any clue where this could come from?

The page I need help with: [log in to see the link]