If you have linked your game account to Facebook, then there will be no problem in restoring your progress any time.
You will only need to follow the indicated steps below depending on your current platform:
1. Completely re-install Brave Frontier (iOS)/Clear Cache of Brave Frontier App (Android).
2. Make sure that your Facebook account (the one linked in Brave Frontier) is currently logged in your Facebook app.
3. Launch the Brave Frontier app.
4. Choose the Facebook Login.
After following the said method, kindly wait for a while as the app automatically restore your game progress. If if you have failed to restore your progress please do not hesitate to contact us so we can help out. Send us a message via our Game Support page.