Shouldn't "NICE" be accepted as dobrý?
It could. As a native speaker, I personally think, it should by tolerated. But "nice" is usually translated as "milý".
So "člověk" is a male word (considering "dobrý", not "Dobrou")? Interesting. The equivalent word in my native language, Brazilian Portuguese, has only female form.
člověk (cf. Latin homo - Portuguese homem?) is maculine
osoba (cf. Latin persona) is feminine
Proc nemuzu tam napsat "kind person", prosim?
It could work, but kind is usually translated as "laskavý".
So you should really use the word "dobrý" which is the most accurate translation.