[Rainbow six siege] steam folder to uplay folder?

The situation: I want to play that game with some friends of mine, but i have a realy slow network, to download 31GB it will take ~10days or more, and a friend of mine have that game but on steam, while i have that game on uplay.
The problem: In the beginning i moved the folder to uplaygame directly, and clicked download, but it start downlaoding the whole game (32Gb) tried to locate it, it keeps saying (Failed to validate game files)
If you can help me with anything, please post below.
Thanks <3