I took over a Xamarin project that was previously outsourced to a 3rd party. Oh boy, what a nightmare. There is a portable c# project that is refrenced in a separate Android project. Whenever I try to fix the broken reference I'm getting this error message:

Taking a look at the project properties, I can see that there is nothing targeting Xamarin.Android which I'm assuming should definitely be there since this library is clearly being referenced in a Xamarin project. By the way, there is a separate project for iOS that also references this portable library so I'm assuming Xamarin.iOS will also have to be targeted. Completely baffled here all information from Google has been useless.
I have looked at:
- https://learn.microsoft.com/en-us/dotnet/framework/cross-platform/portable-class-library
- https://lastexitcode.com/blog/2014/11/16/InstallingPortableClassLibrariesForXamarinStudio/
and all related linked in those pages and endless google searches frustratingly obscure topic.
Taking a look at the packages.config I can see these types targeted as well but again have no idea how these are linked to this package.config.
Are my assumptions correct and how on earth can I add these targets?

