Ok, how does this mean they can reach us? does chegar até mean to reach?
Preciso chegar até o topo = i need to reach the top. /agora que cheguei até aqui = now that i got to get/arrive here....
Yes, I can see "chador ate' topo = to reach (or arrive) at the top. However, "pode chegar ate' nose = can reach (or arrive) until us" is still a bit confusing or me. Can you define ate' is this case, please? And, would the use of "atinger" be inaccurate as a substitute word?
Here it would be "they can come to us/look to us", as we were open for discussion.
"Atingir" is more likely to be used when you have a bullet and a target. =)
I think the objective case ("nos") should be used in place of "nós".
"Eles" // subject
"podem chegar até" // verb phrase
"nos" // object
Nope, this is a different type of pronouns, called prepositional pronouns (since they are the object of a preposition), which you should use after other verbs that call for prepositions (the first and then most emblematic/common example in the Duo course is gostar [de]).
You can read more about them here: http://www.nativlang.com/po/qg_pronouns_prepositional.html