3. (To) Twist someone’s arm: To twist someone’s arm literally means to take a person’s arm and turn it around, which could be really painful if you take it exactly word for word. If your arm has been twisted it means that someone has done a great job of convincing you of doing something and if you manage to twist someone else’s arm it means that you’re great at convincing them and they’ve finally agreed to do something. “Jake you should really come to the party, it’s going to be so much fun and there’s going to be many pretty girls there.” “Pretty girls? Okay, you’ve twisted my arm, I’ll come!”
4. (To be) Up in the air: When we literally think about something up in the air we have the idea that something’s floating or flying in the sky, perhaps an airplane or a balloon. But really if someone tells you that things are up in the air it means that these things are uncertain or unsure and definite plans have not been made as yet. “Jen have you set a date for the wedding yet?” “Not exactly, things are still up in the air and we’re not sure if our families can make it on the day we wanted. Hopefully we’ll know soon and we’ll let you know as soon as possible.”