fudan kara, kono atari wa shizuka na no desu ga, Kimi-san no inakatta 1-shū-kan mo nani mo kawari wa nakatta to omoimasu yo.
Transcript translation:
This area is normally pretty quiet, and I don’t think anything changed while Kimi was away.
I'm having problems with almost every part of the sentence. Starting from the beginning:
fudan kara
Fudan means "usually". I'm guessing "kara" in this context means "up until now". So, "Until now, usually..."
kono atari wa shizuka na no desu ga
"this neighbourhood is quiet"
However, where does the "no" in this section come from? What is the purpose of it? Why not just say "shizuka desu ga"?
Kimi-san no inakatta
I've don't think I've ever seen "no" in this context either. "Kimi-san's wasn't here (inakatta = negative past of iru, right?)" Is that correct? Why is "no" used? Why not "ga"?
1-shū-kan mo
"one week too" which, combined with the previous section, is pretty easily translatable as "the week Kimi was gone too"
nani mo kawari wa nakatta
"nani mo" = "nothing"
"kawari" = "change"
"nakkata" = This word isn't in the vocabulary section, I'm guessing it is a suffix modifying the "kawari" to turn "change" into "did not change." Why not just use "kawaranakatta"? I've never seen the ~masu stem ("kawari") followed by "wa" and then a suffix before. Does this rule work for all verbs? Does it work for all suffixes? Can I say "kawari wa masu" to mean "will change"?
to omoimasu yo.
"I think."
So...
"Until now, usually this neighbourhood is quiet. The week Kimi wasn't here [was quiet] too, nothing changed, I think."