What if (we / you) (did something)?

The question "What if we ___?" is used to suggest doing something. When you say it in this way, it sounds like you're suggesting a new idea that you had. It also sounds like you're only suggesting one possible way of doing something, but you haven't decided that it's the best way yet. Some examples:

What if we offered a two-for-one deal?

You can also say "What if you...":

What if you tried applying for a job at a nursing home?

put (one's) hair up

"Putting your hair up" means styling your long hair in some way so that it's not just hanging down on its own. Some different hair stlyes that are considered "putting your hair up" include:

• putting it in a ponytail
• putting it in a bun
• braiding it

The opposite action from "putting your hair up" is "letting your hair down".

You can also "wear your hair up" or "wear it down".

a (hair) bun

A "bun" is a kind of hair style in which you tie your long hair into a kind of ball shape on the back of your head, usually near the top.