Problem with binding a Xamarin Forms iOS library with objective Sharpie

Question

I am currently trying to bind the following iOS SDK to use it in a Xamarin project: http://github.com/emartech/ios-emarsys-sdk

Android worked, but with iOS I have some issues.

What I have done so far:

1. I copied the source files into a Static Library Project, build with iOS Simulator and iOS Device was successful (arm64 and x86_64)
2. I combined the two a files to a Fat Library.
3. I run objective sharpie to generate the ApiDefinitions.

My problem now is, that the .a files are quite small (only 4kb each) and the ApiDefinition only have 1 header (the default one that was automatically created from the Static Library). All other headers are missing.

Do I have to add them somewhere explicitly? If yes, how?

Thanks in advance!

I tried to copy the files from the subfolders to the main folder but without success.