Optimizing a Joomla-based site for mobile platforms

Hello,
I need to optimize the site based on the latest version of Jumla for mobile platforms. The Protostar template, which should be left, should be modified (that is, the use of templates from other manufacturers is not desirable, only if there are no other solutions to eliminate problems)

All problematic details in the screenshot, but the most important is “Remove JavaScript and CSS from the top of the page that blocks the display”

It is also possible to solve another way, for example, installing some additional plugins or something else.