Besides the bug of the tutorial level others are mentioning, the game feels sluggish because of the low walking speed, slow reload speed and the camera movement when walking which make point at the enemies kind of annoying, you have to tweak those things otherwise the game doesn't feel right. I almost 100% sure you're taking inspiration on Hazama Queen, so try to copy that walking speed and camera movement and your game will improve a lot. My favorite weapons are the shotgun and the melee knife, specially the melee knife because oneshotting enemies it's fun.