How to Backup & Restore Steam Games Easily
Backup files (folders) can be copied to an external hard disk or flash disk, then moved (restored) to another device that also has the Steam Client installed.
How to restore Steam games
To perform a restore, open Steam Client > Steam > Backup and Restore Games > Restore a previous backup > Select the backup folder location > Select the game you want to restore > Wait for the process to finish.
If it has been restored, then the settings and progress in game will be the same as when backed up. The restore process can indeed take a long time, but it’s far more efficient and faster than downloading directly from Steam.