Broken links help with site

You could use your text editor on your theme and plugin files to search for the /js/respond.src.js in the source code.

If in a theme, then create a Child Theme and modify that php file. (Any changes you make to a theme’s code will be overwritten in the next theme update.)

If it is a plugin, then contact the plugin author to have them fix their code. But I suspect the theme code first.