I just started OpenGL programming, so excuse me if this is a silly question...
The problem is, that if you look on my objects you can
easily recognize the quads or triangles.
Here you can see it:
is there a way to make it look smoother without increasing
the amount of polygons?
You could use "gouraud shading" to make the quads less visible. You give each vertex a colour and the colours get interpolated across the tri/quad. If you look in the OpenGL docs and on google you should find plenty of information about it.