"It is necessary that I work a lot."
Translation:Çok çalışmam lazım.
So the structure/logic of this sentence is totally different than the English one. The literal translation is would be something like "My working a lot is necessary" where the subject is "working."
It is the same here. The subject is "çalışma,' which get the possessive ending when you want it to be "my working" :)
Before, there was the sentence "i need to drink water" (using the same "lazım"-construction) and I translated it as "It is necessary for me to drink water", but I was marked wrong for it. Now here we have the same construction and this time it's suddenly correct to translate it as "It is necessary to ..."? I don't get it.