To edit vector files you need to download them as vector assets and not JPEG assets and you need Adobe illustrator at your disposal. As it would be great to have assets broken up in layers, I rarly find that with vector assets. That, however, does not mean that you can't edit the files. Illustrator file elements can be brocken-up and selected up to the primitive graphics used.
Looking at your assets, they don't look that complicated to me. When in Illustrator, I would click on the > to expand the only layer present. Each object in the layer can also be expanded by clicking the > near to that object. I would refer to the Illustrator forum and to the tutorials on Illustrator for further questions handling those elements.
ABAMBO | Hard- and Software Engineer | Photographer