Pls post a private message with the URL to your site, preferably a temp login too and I can see what’s happening here. Undoing responsive behavior can be a tough job at times but hope you can pull this off. I can confirm the location of the responsive.css and the line number for the style.css file too.
Also, several text editors have a function which provides the line number function – pls check the help of the editor you are using. I would suggest you try out text editor like sublime text, notepad++ for this instead of using the system default.