I would not worry about it so much. You are clearly not at this level yet, if you're asking all these questions. A real teacher can help you to progress at the right rate rather than become bogged down in all these tasks which are far too far a leap for you. And no these idioms are not that common. I would use maybe 2 of these regularly ,and the rest no more than once a year in the real world.

They are all common in the US. The first two are new. They have come into use in the last twenty years.

Hi Mari, The first four are all pretty common. The last one is less common and will not be heard often.

Hm...you are asking a tall order^^ But I have some spare time and don't mind trying to help you out. 1. Scold vs. Take someone to task. Scold: 혼내다, 야단치다. You hear and read this a lot among children/students. My mom always scolds me whenever I slouch. Take someone to task: (personally i rarely see this) criticize 2. Shaken up: something really scares or shocks you and so you are still feeling anxious and a little traumatized because of that. Ex) I was really shaken up when I heard a classmate got hit by a train. Caught off guard: something surprises you because you are unprepared. Ex) The pop quiz really caught me off guard. I didn't think our teacher would give us a surprise test today!! 3. Train wreck vs mess: it's really the same thing. Usually train wreck is used when plans don't turn out they way they're supposed to. And mess is just 엉망진창. But honestly they can be used interchangeably. 4. Throw under the bus: you purposefully make someone look bad to make yourself look good. Ex) My brother threw me under the bus and told my mom that I had eaten all the cookies when he ate one too!!! Put someone in a hard/difficult place: You simply put someone in a difficult position/situation but it's not to make yourself look good. Ex) I was put in a difficult place when my best friend and boyfriend were fighting. They btoh wanted me to choose between them. 5. Put off: you purposefully keep pushing back something because you don't want to do it. You are procrastinating. Ex) i keep putting off my homework. I keep putting off my chores. Hold off: push back. you arent purposefully pushing back something but for whatever reason you have to set a new date. Ex) The school decided to hold off the Parent Meeting because too many people caught covid. Since everyone is too busy right now, let's hold off our meeting and try again next tuesday.