You are crazy, thinking that you should lend money to him!
You are crazy, planning to travel around the Earth just in a month!
You are crazy that you said so to your teacher!
You are crazy, behaving that rudely in front of your teacher!
You are insane, thinking of fighting me!
You are insane to fight me!
You are out of your mind to drive from Florida to New York in one day!
Q1) Are these bold parts used as backgrounds for speakers to give opinions of "you" ?
Q2) Are those sentences all natural and grammatically correct?
Q1 Yes, you can think of it that way. Q2 Yes
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.
1) You are [crazy / insane] to [think / plan / drive / ...] ...
2) You are [crazy / insane] [thinking / planning / driving / ...] ...
3) You are [crazy / insane] that ...
1a) It is [crazy / insane] to ...
2a) It is [crazy / insane] thinking ...
3a) It is [crazy / insane] that ...
Of the first three, 1) is probably most used, then 2).
Of course, you may substitut