In the following picture, the parts painted with rust protection primer were completely gone due to rust and are replaced now:

The edges of the part that holds the number plate needed replacements, too (again, see areas painted with rust protection primer):

There is no way to replace the support structure with the outer sheet metal parts in place, so they need to go:

(c)rusty!

It is obvious that parts need to be replaced...

(some numbers are wrong in this sketch!)

After the 3rd iteration...