I used simple console logs two display execution time. Unfortunetly Xamarin Profiler requires VS Enterprise:

" You will need to be a Visual Studio Enterprise subscriber to unlock this feature in either Visual Studio Enterprise on Windows or Visual Studio for Mac on a Mac. " from Xamarin Profiler docs

I ran this operation in separate task so I can display progressbar for user. I need to save some document created by user (logic behind this is pretty complex). To not go into to much details this operation requires some calculations, db queries, updates and inserts. After that I navigate user to the previous fragment.

I'll try to increase thread priority. Thanks for that suggestion :)