Hello!
When in settings, I choose jQuery Version 1.x.x. , then the popup images aren't working (see attached picutre). When I choose jQuery Version 3.x.x. , then popup images are working great, but then publish/save buttons are not working.. What can I do to fix that?
Please help!

Theme only got minimum compatibility to updated jquery versions.
Image library should be fancybox that might be already optimized for jquery 3.x (currently in newer themes fancybox is not used anymore)

So there is no way to get both things to work ?

That theme is after it's lifetime, no work is planned on it.
Try to put older version of fancybox on your osclass (in oc-includes/assets)