The mesh shown in the picture with red marking is incorrect .. you have to add surface boundary layer near the front area and mesh the area finely ...try to keep maximum elements as hex .. it gives proper results
In fact since you are using fluent, there is no need for C type grid.
1. Grid should be rectangular near the body, elsewhere it is better but not necessary
2. if you are solving invicid or laminar flow,try boundary layer near the airfoil
3. if flow is turbulent ( as I think it probably is) boundary layer mesh is not needed near the wall but node distribution should be consistent with your law of wall
4. near severe gradients such as stagnation point a fairy dense mesh may help
Use a good boundary layer mesh (inflation in gambit or so)...check how much of the drag is due to viscous forces and how much for pressure... If separation occurs check the different turbulence models and wall functions. good luck