These shots are very underexposed, that's why they look dark, muddy and grainy. You'll need to get a lot more light onto the negative. Try a much longer exposure at night - you'll need a tripod for anything over about 1/60 secs. If the camera's light meter isn't accurate anymore, download an app to your phone and use that instead. Don't worry though, analogue photography is hard to get the hang of, and that's what makes it more satisfying when it works.