whats the meaning of this idiom:
(this is the last thing i need)
A person who is already facing some troubles of some sort has one more bad thing happen. What they really need is help, not more trouble. More trouble is the last thing they need.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.