Change Gallery

Hey there!
Freshly bought and installed I aim to place an individual gallery in the beautiful Qusq theme, popping up each time when a project-title-picture on the home page is clicked. Instead by default (“regular images – pop-up image” is activated) a gallery shows containing all the projects title images.
(The site still contains all the demo content)
How am I to change that the way I want to?
This is fundamental to my vision of how I want my portfolio to work.
Thanks and cheers from Berlin
max