custom css file is not working

If you’re referring to the custom-responsive-d1643baadca4389e9e5c9267529c352b.css file in your theme, it’s loaded on mobiles all right, but many of its rules are overwritten by other rules so you may not see the desired effect. Use your browser’s element inspector tool to help resolve the application of the desired rules.

A bit off-topic: You have some sort of CSS and JS injection plugin. It’s being used to inject regular HTML into the head section, which results in invalid HTML. Browsers often interpret invalid HTML as intended so there may be no ill effect, but it’s still technically invalid all the same.