Do you have to bring your own bags

Yes.

You can use a box, don't forget a quarter

Yes. They have very sturdy bags with handles that you can buy.

You can if you want to! It's up to you! They do have bags that you can buy or you can find a empty box

Alternatively, there are always empty boxes laying around the store you can use as bag substitute.

Yes, bring your own bag, pick up a cardboard box in the store, or bring your own laundry basket, whatever you want

Yes, or buy them there.