Conflict between Guava and AndroidX Nuget Packages

I have this Xamarin.Android C# project in where I managed to retrieve my data from my Firestore DB to my app against all the odds from one of Firebase support guys who mentioned a few weeks ago because of Xamarin is not officially supported or something like that.

Anyway, all was working perfectly until I needed to use Google Auth which needs AndroidX Nuget Package in my project, and seems to exist a well known conflict between Guava and AndroidX packages.

So, now I'm having this error:

"Failed resolution of: Lcom/google/common/base/Preconditions;"

In my 'FirebaseFirestore GetDataBase()' function.

Code:

public FirebaseFirestore GetDataBase()
        {
            var app = FirebaseApp.InitializeApp(this);
            FirebaseFirestore database;
            if (app == null)
            {
                var options = new FirebaseOptions.Builder()
                    .SetProjectId("project-firebase")
                    .SetApplicationId("project-firebase")
                    .SetApiKey("ZIzaSyAq55czhZRo00c1JKHHtzdNiIX7vIXu5Iz")
                    .SetDatabaseUrl("https://project-firebase.firebaseio.com")
                    .SetStorageBucket("project-firebase.appspot.com")
                    .Build();

                app = FirebaseApp.InitializeApp(Application.Context, options);
                database = FirebaseFirestore.GetInstance(app);
            }
            else
            {
                database = FirebaseFirestore.GetInstance(app);  //-- ERROR HERE!
            }
            return database;                    
        }        

I tried downgrading Guava to 27.1.0.0. but then another really bad, maybe the worst, error shows up:

"java.exe" exited with code 1.

So I went back to 28.2.0. Guava version, and long story short I'm stuck.

Could you guys please help me to find a workaround to this?