This one's awkwardly translated. Just in terms of translation (it's again not that funny to me), I'd write it as:
A lady enters a gallery, wanting to buy a painting. But she is not satisfied by any of the paintings she is offered by the gallery owner.
, the lady asks, "Why are all the women in the paintings naked?"
The gallery owner says, "Well, if they were dressed than their clothes would just go out of style in a couple of years, right? But naked ladies are timeless..."
:-/ Still weak.
One thing that doesn't make sense to me is that when I think "gallery" and "naked women" I think more classic odalisques et al anyway... things have to be relatively recent to really "go out of style." (I.e. something from the 1980's can look silly now, but something from the 1880's will just look charming and old-fashioned, not "out of style.")
Re: this part:
Feigning that he is unable to do anything with it, the boss replies:"I have no idea about how to improve this. If they dressed, the design of the dress will soon be not in fashion."
I just wasn't able to figure out the intended meaning here. Is it disreputable somehow to have a gallery with images of naked women? And the joke is that the owner is pretending he has nothing to do with the selection of art, when he does?
Definitely one of the weaker ones, probably a cultural element in terms of whether nudity in art is OK or giggle-inducing.