Looks good! Our resident pirate cosplayer has already given some good advice, so I’ll just expand a bit on this bit:
In Japanese, entire clauses can be descriptors preceding the noun they modify, usually when using progressive tense (〜ている) or past tense (〜た).
So for example:
踊っている人間 means “dancing humans”
Or when using past tense:
暗くなった部屋 means “the room that got dark”
You can do this with entire phrases, really. In a construction like 明日買っても今日もう壊れた車, the whole 明日買っても今日もう壊れた part is just a descriptor for 車, so that means “the car that already broke today even though I bought it yesterday”.
You can use the same principle here.
Spoiler in case you want to know how to say “Nessa is the dog I adopted from Romania last year”:
Nessaは(私が)去年ルーマニアから引き取った犬だ
(I used the plain form there, to make it a more polite sentence just replace だ with です)
Not really, it’s a bit strange - you’re essentially saying Nessa is the dog that became your adopted (implied to be human) child in Romania.
で marks the location where an action takes place which might work, but I think the implication is that you went to Romania, adopted a dog there, and then took it back. Might be what happened, but I interpreted it as the dog coming from Romania to be adopted here (not an uncommon occurrence, here in the Netherlands at least - a friend of mine did exactly that).
And 我 is a bit of an unusual first person pronoun to use I think, but I guess that’s not incorrect, just a bit odd maybe 
Also I’m not sure about this but to me using なる feels like taking emphasis away from the act of adopting, almost making it seem as if the adoption was something that just sort of happened.
There is! Well, a word written in kanji anyway: 白鼬