This liink: https://www.acupuncturist-yang.nl/kunst/ produces this output: see screenshot:
https://wppa.opajaap.nl/my-album/wppaspec/oc1/lnen/cv0/ab99/ptKnipsel-china.PNG
It 1. shows the image, and 2. is NOT a full featured slideshow.
I do want to help you, but you make it unnessesarely difficult for me.
You re-enabled the right-button click prevention.
You can fix the menu lay-out problem by increasing the z-index in the css of the ubermenu from 10 to 100. You should also add either position:relative or position: absolute, to make the z-index functional. This may however cause a positioning problem that can also be corrected by css. But now i can not test this for you.
Make sure you clear/re-initialize any caching or optimalization or minification to make sure your mods are effective.
This informaltion should be enough to solve your problem.