“Guys, let's call it a day.”
You're working on a project with a few other people at work. You've all been working hard all afternoon, and now it's getting late. You think you should stop working on it for today, so you suggest this.
Guys, let's call it a day.
In English, there's not a really good word for addressing a group of people. If you're talking to one person you say "you":
How are you?
But there's some disagreement about what to say to a group of people. English speakers use different expressions depending on the region and dialect, but one common expression is "guys". For example, at a restaurant with a large group of friends you can say:
Hey guys, are you ready to order?
"Guys" technically means a group of men, but it's usually OK to use it for mixed groups of men and women, or even for groups of all women.
In very formal situations, avoid calling a group of people "guys". Instead, use a phrase like "everyone":
Everyone, thank you for coming.
Make a suggestion using "let's ___" when you're pretty sure that the people you're speaking to will accept your suggestion. If you're not as sure, you can say "why don't we ___":
Guys, why don't we call it a day.
This phrase, "Call it a day", means to stop what you're doing for that day.
You use this when you're not 100% finished with everything you need to do, but you're tired or ready to go home. Use "Call it a day" when you're working on projects with people, practicing for something together, or just to let people know when you're leaving work:
Jean, I'm going to call it a day. I'll see you tomorrow.