Wouw you pointed me in the right direction. found another jquery.min link in footer.php . it works now!
Now i have only one problem left:
When i try to agree or deny a booking in the admin page, it keeps ‘updating’ .. it did everything it is supposed to, only not refreshing the page..
(https://watertorenlutten.nl/wp-admin/admin.php?page=booking/wpdev-booking.phpwpdev-booking)
I get the following error:
SyntaxError: missing ; before statement load-scripts.php:5
Any ideas?