how to change URL of navigation menu, based on user device? (make it mobile link automatically)

I've been trying to change a URL for one of my navigation menu from Pc version to mobile version, based on user device.

The code below is how I tried to do it. In the screen below 600 px, I specified to redirect to the link inside content: url("");, but it doesn't seem to work. 

@media screen and (max-width: 600px) {
  .Header-nav-item--external
a[href="http://www.chamdoctor.com/re/sub09/sub09_02.html"] {
    content: url("http://m.chamdoctor.com/sub04/sub04_03.html");
  }
}

@media screen and (min-width: 601px) {
  .Header-nav-item--external
a[href="http://www.chamdoctor.com/re/sub09/sub09_02.html"] {
    content: url("http://www.chamdoctor.com/re/sub09/sub09_02.html");
  }
}

7 hours ago, YKL said:

I've been trying to change a URL for one of my navigation menu from Pc version to mobile version, based on user device.

The code below is how I tried to do it. In the screen below 600 px, I specified to redirect to the link inside content: url("");, but it doesn't seem to work. 

@media screen and (max-width: 600px) {
  .Header-nav-item--external
a[href="http://www.chamdoctor.com/re/sub09/sub09_02.html"] {
    content: url("http://m.chamdoctor.com/sub04/sub04_03.html");
  }
}

@media screen and (min-width: 601px) {
  .Header-nav-item--external
a[href="http://www.chamdoctor.com/re/sub09/sub09_02.html"] {
    content: url("http://www.chamdoctor.com/re/sub09/sub09_02.html");
  }
}

 

Can you share your website URL?

34 minutes ago, Web_Solutions said:

Can you share your website URL?

Sure, Here it is.
https://chamdoctor-jp.com/

As I mentioned, I want a URL of the link menu in the navigation to change to a different URL only on mobile devices.

As is : 
Link of Navigation menu (症例写真) : 
http://www.chamdoctor.com/re/sub09/sub09_02.html > on PC
http://www.chamdoctor.com/re/sub09/sub09_02.html > on mobile

To be : 
Link of Navigation menu (症例写真) : 
http://www.chamdoctor.com/re/sub09/sub09_02.html > on PC
http://m.chamdoctor.com/sub04/sub04_03.html > on mobile

Sir, you saved my day. Thank you so much!

12 minutes ago, YKL said:

Sir, you saved my day. Thank you so much!

Welcome