visual studio does not save the changes in the frontend

Next to the execution button there is one of "Refresh" if you click on the drop-down menu it will give you some options to refresh the files.

Now if doing this still does not refresh the files you can press the shortcut Ctrl + F5 in the browser which will force you to refresh your files.

This is a problem of caching , which browsers do by default not to reload files that "already" have, you do not say that you are using exactly but if you are using aspx you can do the following:

<link rel="stylesheet" href="css/mycss.css?v=<%=DateTime.Now%>" />

this will change the version of the file every time you do F5 in the browser causing it to think it is a new file and download it, beware this is used in development mode but in production this is not used because one expects the browser to do the work of caching

I hope this greetings will help you