Be one card short of a full deck phrase informal
To be unintelligent or mentally deranged.
She was one card short of a full deck and always thought everyone was trying to kill her.
Nick said that he liked standing under a tree in a thunderstorm. I think he may be one card short of a full deck.
He was one card short of a full deck, but he was industrious.
Extremely stupid
Very stupid, or silly
To be extremely stupid; not to be alert
(n): a fool person,
(adj): stupid, foolish, silly
The verb "be" should be conjugated according to its tense.
If a person has the devil's own luck, he or she has extremely good luck.
A: Yesterday I won a $10 million lottery jackpot and today I won a car in a draw.
B: You have the devil's own luck.