Hei, My biggest project was with Xamarin :-)
I will find the crush point, and tell you exactly what is the problem, and fix it if you want.
About the slowness, it depends: does you app use multi threads? If yes, I assume I will find the problem quickly.
Otherwise, slowness can appear of many other reasons, which I explore and find the root for it.
Have a nice day,
Itzik.