Hello,
I'm UI Designer and I have experience on working overseas, I know how to prepare the material for a developer I'll never meet. I already did a lot of Apps for iOS & Android, also cross platform.
I can't attach here my portfolio because it's an offline portfolio (most of my work is confidential or still not published, thats why I have to show it offline, I hope you understand).
If you want I can send you my work on wetransfer.
Thx for reading