In order to remove circles animation, please find the particles-js class and remove it from a file.
And add for the required section one of the three classes:
static-circle-bg1static-circle-bg2static-circle-bg3
These classes differ in the location on the screen, namely have different placement of background images.
Each of them has a predefined static background, please, select the one that most relevant for your tasks.
Circle animation - "background-parallax" in footer section
If you want to deactivate the background animation and leave the background as a static, you just need to remove only one scene class from the markup page:
<section class="сrumina-parallax-background"><div> <div data-depth="0.2" class="layer first-layer"></div> <div data-depth="0.6" class="layer second-layer"></div> <div data-depth="1" class="layer third-layer"></div></div></section>