Pages simply do not load all at once. They all follow a specific loading sequence. However, there are measures you can take to make the experience less jarring to the end user.
One is to reduce the number of supporting file requests needed. You have a lot of script files for one thing. See if your caching app has an option to combine script and CSS file content to reduce the number of requests. If not, try one of the file optimization plugins that will do this for you. Note that in some cases combining files will cause script errors or cause scripts to malfunction. It may not be possible to combine files in some situations. It’s worth trying it to see if it does work without causing errors.
The jarring load experience is largely due to really large layout shifts. This is the main issue you’ll want to address. A large part of the layout shifts is because various elements do not have height and width attributes which help the browser reserve space for these elements before they are fully loaded, avoiding many of the shifts. Use the Google Page Speed Test or the Lighthouse developer tool in Chrome browsers (they both use the same underlying analysis engine) to see which elements are missing size attributes.
You’ll also want to address the other “Opportunities” the tool calls out, as well as some of the “Diagnostics” things the tool had flagged. Some of the issues flagged may not be that easy to correct, but at least address the issues that are somewhat easily fixed.