Probably something in Linyphiidae, mostly going by the eyes. They are notoriously hard to identify because they are so small and there is so many of them.
How does one identify without using AI? Do I need to buy a book or are there good material online?
Books are great start, I have 3 field guides here, they are great for narrowing down an ID. They also provide detailed descriptions of distinguishing features that aren’t obvious in pictures. But they tend to get outdated in the long run. But still useful, if you keep up otherwise.
Next best things are online resources that are run by professionals. This is my main online source for European spiders: https://wiki.arages.de/index.php?title=Hauptseite
Other than it, for me it’s just experience. I’ve been doing online spider identifications for over a decade now, met a lot of people way smarter than me that helped me out, corrected me and thought me stuff over the years.