The Lag and the RAM Issues seem to be gone, but my PC is acting up a lot generally this morning, so I'll try and give it more of a play this Evening.
So far, it's incredibly dark and hard to see anything, but that might be due to the current Lighting conditions at my Place aswell.
Your Doors have a very small interaction Box only at their Doorknobs it seems, so you have to stand pretty accurately to move over into the next Room. I also liked/like your Camera a lot more when its in the more traditional RE-Style like in the Foto-Section, or previous DDs. It also works a lot better for your Playermodell, which looks like a nice abstraction then, but more like a very roughly formed blob up close.
Your Camera Controls in Third Person are really Janky and just feel wrong, and you don't lock the Mouse to the Screen during Movement aswell.
If you're using render Textures for Inventory Items etc., consider rendering them all out only once at level load, or even prerendering them before building your Game and keeping them as static Assets. If they don't rotate, but only scale/move, you can save a lot of performance by not constantly rendering the same Texture again and again.