No worries! First of all make sure that your geometry is watertight as well as avoid overlapping surfaces! I can see some overlap in the front of your car for instance. Decreasing the number of cells was just mentioned as you have way too much cells at the moment (as you noticed it takes very long to load the mesh) - so lowering the refinement levels can definitely help! Maybe our @PowerUsers_CFD can give you some additional tips on your issue.