Hey @Victor_Escobar_Olmos and @Kenan_Casey, we published a new build of Backendless SDK for .NET, version 5.3.0 to Nuget. This build fixes the problem with dependencies when creating a .NET Standard project (i.e. a Xamarin Forms project). Please update your NuGet dependency for Backendless to 5.3.0.
Cheers,
Mark