"It is over here."
nope! the meaning is a little more specific with arimasu, but they'd both be fine as an answer here
「ここにあります」 " 'here' is the place at which [the subject] exists"
this would answer "where ARE your keys?", but I don't think this would answer the question of "where do you PUT your keys?"
「ここです」 "[the subject or the location of the subject] is this place"
I believe this would answer both of the previous questions, but I'm not completely certain that it would feel natural as an answer to "where are your keys?"
if a more experienced speaker has any corrections or feedback, I'd love to hear!
My ここです was marked wrong by Duolingo, in spite of it being among the suggested answer in the hover-over hints.
Then again, Duolingo wrong/accepted results being complete rubbish and completely random is something i should get used to, I suppose.
ここ に あります is always correct, as ここ simply means "here" - a place. こちら can also be translated into English as "here", but in the directional sense. A more literal translation would be "this way" (well illustrated by its now practically obsolete kanji: 此方 ). こっち is the casual version of こちら, and Duo tends to mark casual speech as incorrect either way (so far it's only teaching polite speech).
「が - ga」and 「に - ni」are Japanese particles. Japanese particles are small words, that indicate words' relations within a sentence. Most particles have multiple uses.
The particle 「が」can be used to introduce a new subject. For instance: アイスクリーム「が」あります。 Meaning "There is an ice cream."
The particle 「に」can for instance be used to indicate a location when combined with the verbs いる or ある. For instance: ここ「に」あります Meaning "It is over here."
If you want to know more about particles, then this link might be helpful> https://www.japanesepod101.com/japanese-particles/ (It's also my sauce ;3)
Short answer: が is used to say this object exists! While に is used to describe a location. (≧◡≦)
ここ means "here".
"this" would be これ or この, respectively.