If your game download is going more slowly than normal on the Steam client it is possible the download server you are currently using is experiencing a high volume. ( this can happen most often on big releases. )
You can check the Status of Steam Download Servers HERE.
To change the download server for your game, first click on Steam > Properties at the top of your steam window.
in the settings menu, Go to the Downloads tab, your download server will be located just to the right. Make sure to select a region fairly close to you!
For further assistance with the Steam Client, we recommend contacting Valve’s support team HERE.