Have lots of edges in my starship mesh, as shown in the red box.
How could I reduce them and make one rounded face out of it?
i don't think it is possible to have a curved face without the extra edges. more vertices and edges add more resolution/detail to the model. you could try selecting the faces, pressing x and selecting dissolve faces.
Just as Tainin said it is not possible to make a curved/bent/folded surface without joining two or more vertices with an edge. However you can make a low Poly model and use smooth shading (in tools menu) to give a more curved shade effect. Or perhaps the normal maps might help depending upon the purpose of your 'Ship'.