I think that 偏偏我 exactly means "me of all people". This means the same as "unfortunately only me", but the wording is different. So, I think that : 大家的行李都没事，偏偏我的被弄丢了 could be translated as : "Everyone's luggage is fine, but, of all people, mine got lost"
你究竟懂不懂我在说什么？ To translate this, I would add "so" at the beginning of the teacher's text and say : "So, do you understand what I'm talking about?" This "so" indicates that all discussion is over, and we just want the final outcome. This is how 究竟 means "finally", "in the end", or "when all is said and done".
I think that 偏偏我 exactly means "me of all people".
This means the same as "unfortunately only me", but the wording is different.
So, I think that :
大家的行李都没事，偏偏我的被弄丢了
could be translated as :
"Everyone's luggage is fine, but, of all people, mine got lost"
Still feel confused about 究竟。I don't think it was explained clear enough on it's meaning as a noun or it's usage.
你究竟懂不懂我在说什么？
To translate this, I would add "so" at the beginning of the teacher's text and say :
"So, do you understand what I'm talking about?"
This "so" indicates that all discussion is over, and we just want the final outcome.
This is how 究竟 means "finally", "in the end", or "when all is said and done".