Quote:...Would it be possible to make everything black and white besides the butterfly?...
If you go here https://www.gimp.org/tutorials/Layer_Masks/ At the end there is an example of a desaturated background.
Edit: FWIW - Do you have a larger version, that image is very small. Because of the size, it is as easy to use the clone tool to remove the stick and its shadow. However
Duplicate the layer, desaturate the top layer, add a layer mask (white) make the layer mask active and paint in the layer below.