On the back burner

If you put something 'on the back burner' (which is the back part of the stove), it means that now you have to attend to other things first before you can get back to it.

Example:
-I was planning to replace my kitchen floor this summer, but now we have to get a new car.
-Well, I guess the floor will have to go on the back burner.

To go off on someone

'To go off on someone' means to tell someone how angry you are about something they did.

Example:
-So what did she say?
-She totally went off on me, saying how immature and irresponsible I am.

On the same page

Being 'on the same page' is a phrase used by one person to reassure that the listener is in agreement with them about something, understands or is thinking about something in the same way. It is usually used after there has been some discussion about something and an agreement has been reached.

Examples:
Okay, let's make sure everybody is on the same page. We'll meet back here tomorrow at 2:30 for rehearsal.

-Carol really needs to go to the doctor tomorrow. I think we're all on the same page about that.

C'mon!

'C'mon' is an expression American English speakers use to try to encourage someone else to do something. It's short for 'Come on.' Most speakers say the abbreviated version unless they are in a more formal setting, or if they are angry and want to add emphasis to each word to show their frustration.

Examples:
-C'mon, Mom! Please?!

(Person is stuck in traffic behind a very slow car) -COME ON!