I visited your shared site and found you are facing this issue because you are using custom solution posted in the below topic to make the top level menu link work.
https://colorlibsupport.com/t/correct-menu-structure/page/2/#post-28178
To resolve this issue please remove that solution and use the custom plugin solution shared in the following topic.
Also I’ve got a question concerning changing the footer (in my child theme – changes for activello itself work perfectly fine as you can see, but I want to include the code into my child theme so I don’t have to change it after updates) – should I request this in another thread?
Yes please ask it in new thread here Activello - Colorlib Support Forum