You can transfer your game progress from a mobile device to PC by linking it to My.Games.

Firstly, follow these steps on your mobile device:
1. Open the Settings menu in the game.
2. Switch to the Sign Up tab.
3. Find the My.Games linking and press Enter.
4. Create a new My.Games profile or use an existing one. Make sure to use that My.Games profile, which does not have any other game accounts linked to it.

After that, do the following on your computer:
1. Install My.Games Launcher if it is not installed yet (download it).
2. Log in with the same My.Games profile which you used when you linked your game progress on the mobile device previously. If you used an e-mail, enter your e-mail. If you used a social network, log in with it.
3. Install Left to Survive.
4. Launch the game.

If you want to transfer your game progress from PC to a mobile device, you need to log in on your mobile device with the same My.Games profile, which you use in My.Games Launcher on your PC.