Disable mobile version (css)

I’ll assume you mean to remove the responsive side of the design. Theirs no real way to disable the css, rather you’ll have to rewrite the css code or at the very least delete it (deleting isn’t advised as updates will just re-add it which will be a pain)

Do you know css at all and how to make a child theme? If so you can setup a child theme and new style.css and add media tags to adjust the mobile css values to the desktop css values

look for something like this

@media only screen
and (min-device-width : 320px)
and (max-device-width : 480px){
/*Css Style code*/
}