:: published that Melania was a prostitute and it is proven to be false, Trump has a good case ::
No!
DJT does NOT have a case in any sort.
Melania has a defamation tort. She does not need her husband’s finances to bring the tort as she is a court recognized entity.
She is a businesswoman in her own right and can rightly bring that tort on her own effort and may win.
It all depends on court ordered exposure of evidence.
Trump (Melania) has a case and I would think Donald or his lawyers could help with that.