Help with my skateboard

Hi Supost,

I have a starter longboard I've been messing around with for a while. Recently, one of the wheels has started rolling really slowly. I don't really know anything about skateboard maintenance and was hoping some skateboard aficionado could give it a look and give me some tips on how to fix it and up and keep my ride in good shape. There's a coffee or beer in it for the good skateboard Samaritan who helps me out.