Here is an easy guide on how to install pirated games directly from steam into your system.
Go here download this and install After installing steamtools, goto SteamDB it should look like the image below
search the game you want, in my case it’s boderlands 4 and copy the App ID
after copying the App ID from SteamDB go here and paste the App ID
download it and open steamtools, drag n drop the .lua file.
steam will show you the game there in your library now and you’re good to go. enjoy your games :).