I've found it very difficult to find stories with a female protagonist and a solid magic system.
A few ideas:
You don't have to buy the whole series. Try the first book. That will give you an idea of how much content was skipped.
If you are still hesitant, you can try the first couple of chapters of the LN for free here. That will give you an idea of how much is cut down.
All of Kumoko's (spider girl) monologuing, her planning, her fights, her skills, and on. In other words, a lot of her characterization, as well as foreshadowing for future events. They also cut out a lot of the human side of the story. It was always a side thing, but it's even more so in the anime. They also cut out a lot of talk about how skills work, which is important. For example, the "Ruler" skills have mental effects, which is part of the reason for Kumoko's behavior changing partway through the story.
One of the best isekai releasing in English right now is “So I’m a Spider, So What?” . It starts as a pretty solid survival isekai, then becomes something special
I guess you could make an acc on German Amazon and purchase it there?
Digital copies here
Kobo: https://www.kobo.com/us/en/ebook/so-i-m-a-spider-so-what-vol-1-light-novel
Bookwalker: https://global.bookwalker.jp/def5d42977-16d7-43c5-a9be-5b4f1821272f/so-im-a-spider-so-what-vol-1/
See the FAQ for other options.
Volume 1 is ideal. I wouldn't recommend starting after volume 3. If you really want, volume 6, but I'd advise against it, since the anime skipped a lot of important things.
Kobo: https://www.kobo.com/us/en/ebook/so-i-m-a-spider-so-what-vol-1-light-novel
Bookwalker: https://global.bookwalker.jp/def5d42977-16d7-43c5-a9be-5b4f1821272f/so-im-a-spider-so-what-vol-1/
Exactly. Light novels might have the odd picture or illustration inserted, but the bulk is just text.
Check out this Amazon page and click Look Inside for a sample.
It is advised to start from the beginning:
https://www.amazon.de/Spider-What-light-novel-English-ebook/dp/B0723G97LX