“Go right ahead.”

You're in a coffee shop. Someone asked to use the chair next to you by asking "Is this seat taken?". You're not using it, so you say:

Go right ahead.

Go right ahead.

This is a set expression that you say when someone asks you if they can do something and you want to say "yes". "Go right ahead" sounds polite and a little formal. You can use it in situations like the following:

• When you're at the gym and someone asks to use an exercise machine that you just finished using.
• When you can't open a package and your friend asks if he can try to open it.
• When a family member wants to do something that you think is a bad idea. You want to tell them that they can do it, but you also want to show that you don't think it's a good idea.

The last example carries a slightly negative sound. People sometimes use "go right ahead" in this way to show that they don't like what someone is doing.