Open theme folder > page-work.php line 12, change the ALL with yours or remove it if you dont want to use ALL.
Then open theme folder > js > main.js line 133 or search for " loadPortfolio("all"); " change that "all" word with your specific category. Also in line 164.
after that you need to change the use infinite scroll in page option > work template to "NO".
P.S : if you use infinite scroll it will load image after scrolling the windows. If you use masonry template, this trick also will not work.