One second is quite a lot. But there is no way in hell you are saving 1s just because Google "says so". Here is my network inspector, with cache disabled from a 2016 macbook laptop, from Thailand (quite far away from your server). As you can see, your "document" output is the first big load time taking 683ms, whereas the CSS loads at 43ms (which is quite far away from Google's proposed 1080ms):
What do you see in Google inspector?
Of course, these values might fluctuate depending on many factors, but Google "defaults" are way off target. Besides, they base their suggestions as if a site is something like cnn.com or bbc.com ... Those websites need to squeeze every single byte to get to first visible readable text, because they have millions of readers every day, for example sitting on a morning train viewing from mobile. Every millisecond counts, and rightly so. This does not apply in the same way for a portfolio website, and that's why I don't comment on the output it produces.
All I can say, you need to check your website as a HUMAN, preferably on both desktop and mobile. Does it seem slow (compared to the type of content and compared to other websites)?
hochzeiten.danielbollinger.de ... X3 has been optimized for speed in real life for humans.
I could go on and on about what Google reports ... How does it know we aren't using the CSS later on in X3? Google doesn't even know that X3 is dynamic website that loads the CSS only once, and does not need to load it again when navigating pages. Thus X3 does load a fair bulk of resources up front, but it's ultimately beneficial. Of course, there is always room for improvement, but in terms of what Google is reporting here, it can't be used for anything meaningful.
Essentially what many load-critical websites are doing right now, is that they place some "critical" CSS at the top of page, necessary for the page to display. This would be news websites etc. Then as the page is displaying, it can load all non-critical CSS. Considering how fast your CSS file will load in the first place, and considering how small percentage of your website's load time this takes, it's not a crucial part. Most importantly is to get page/document output served as fast as possible (as this blocks all other loads, and is often the slowest resource), as well as
optimizing your images ... What's the point of saving 30kb on a CSS if you have an image that is 1000kb and can be compressed down to 500kb?
Google pagespeed (and many similar) are very inaccurate and often give an unbalanced view of your website's loading. They consider all websites as if they are news-website, where every ms and byte counts, and correctly so, because the aim is for the visitor to be able to read that first word.