Thanks to all for the complimentary words.
Thanks to the designer of the model. It is a really nice model where some details could be added as mentioned before. Also the body was too weak to stabilize the wings (160mgr paper).
As mentioned before I used spar varnish as a try to stabilize the body ....and it worked - the body has become more stable and the wings are in place.
Furthermore this step made a new shining look - I will post a photo this evening.
@ details - I will not touch this model, but I am sure that I will do it a second time and then I will change the cockpit, the back plate and the droid plate.
Last thing: I found a lego model of bb-8. Some light changes and it can be used for this model.