From the comments:
But my point is, that I do not really want feedback on how to write the code. I want feedback on the api and documentation. Like, do you see why the library is useful? Are you able to use from the examples provided?
That actually changes things. If you don't want a review of the code, what do you expect from a site called Code Review? If you're looking for opinions on user-friendliness, try a forum where soliciting for opinions is widely accepted. It doesn't fit the Q&A style of Stack Exchange, not even on Code Review where we're somewhat lenient in that regard.
Here, we can help you with how it's written and in part how to make it more user-friendly. But asking specifically about its usability smells like a design review to me. Programmers might be able to help you with that, but it's too general for us. Too high-level. On this site, details matter. And it doesn't sound like you're interested in the details. You're not at that stage of developing your library. And that's ok. Feel free to come back once we can do something for you.