While Steam’s Backup and Restore feature is reliable, it is really slow and will take more time than usual copy paste. If you’re okay with working a little more and take manual backup then head below and follow our guide for the same. Moreover, it has been a while since Steam updated their Backup and Restore feature which makes it a little slower than the usual copy paste of game files.
How to manually Backup and Restore Steam Games

1 Go to the Steam Installation folder. For Windows 10, the default path is “C:/Program Files (x86)/Steam/steamapps/common”.
1 The folder will have sub-folders with all the installed games. Most of the games will carry the original name while some might be abbreviated.
1 Select the games you want to backup and copy them. Now paste them into another folder or drive where you wish to take the backup.

That’s it. This should backup all the game files to another drive. Make sure to backup the save files from Documents as well.
How to manually Restore Steam Games

1 First copy and paste the games you wish to restore to “C:/Program Files (x86)/Steam/steamapps/common”.
1 Once done, open Steam and select the game and click Install.
1 Technically, Steam should start downloading the game at this stage but it will run a check for the game files first and since they are already there, the game will be installed directly instead of downloading. Although, it might still download any new updates which were not the part of the original backed up folder.

Also, make sure the install location and the location where you pasted the game matches else it will start downloading the game again.