With those specs, Desktop - High might be pushing it but Standard should be doable. Shadows and lighting have the biggest performance cost, so minimize those as much as you can. Make sure you're not running anything else in the background while you play -- close all other programs and put your virus scanner into passive or game mode (if it has that feature). Make sure you have the game set to Full Screen, not Borderless Window or Windowed. And make sure the game's resolution is the same as your monitor's native resolution. Finally, make sure all your drivers are up to date.

Your hardware is a decent mid-range spec - you should be able to get a playable frame rate on Desktop - Standard. If you can't, something else may be causing a problem.