Here's Your error:
on each page its own set of css. You can do each just the right feed to the browser's css file. But since browsers cacheroot resources such as css, it turns out that it's less optimal. 1 cached file with all the css often works more quickly and reduces the requests to the server than a lot of small, but "requiring myself to upload".
There are many really intelligent optimization and you can write a book (critical css + asynchronously rest, etc.). But in short:
look in the direction of gulp, bundling and minification of css and not separation.