1- "HIER sind keine Ratten" = "There are no rats HERE." (btw: I don't see here "there are")
Hier = here = aquí; Literally it would become
Here are no rats, but in English this construction is unnatural, so we turn it around, putting
here to the end and adding a dummy subject
there to the front. This "there" does not mean "over there" (allá), but instead "there are" is equivalent to French "il y a".
I hope this helps clear up your confusion over why "sind" becomes "there are". This is more an English problem than a German problem.
2- "Es sind keine Ratten DA." = There are no rats THERE." ...why not: "DAS sind keine Ratten" ?
Das sind keine Ratten would mean
Those are no[t] rats [they may look like rats but are actually hamsters].
Das = That/those; Da = There [in the sense of
over there (allá
)]. In the sentence "There are no rats there" we have two
different uses of
there, the first is part of "il y a", the second is "allá".
But you could say "
Da sind keine Ratten", which means the same as "Es sind keine Ratten
da", except that it focuses more on the place than on the rats.
"Ratten sind da nicht" = "There aren't any rats" and I have also read that it means "Rats are not there" ? (post #8)
"Ratten sind da nicht" or "Ratten sind da keine" is a changed word order from the original "Da sind keine Ratten"; it changes the nuance of the meaning. See post #7.
But "Rats are not there" is not a natural thing to say in English, so your question in #4 (answered in #8) is pointless (if we never say it, it doesn't matter what it means); you could say "
The rats are not there", but that would refer to a
particular group of rats.