Let's say there is a business selling shoes. They want to accept Bitcoin. How do they get set up to make this work in the real world?

I would assume that for every purchase, a new QR code is created for individual transactions.

I have sent bitcoin to my siblings through Mycelium. When I did the transaction with my sister, it showed that her Bitcoin was pending verification within 5 seconds of me hitting the send button on my phone. The next time I sent Bitcoin to a my brother, his app took about 3 minutes to show the transaction was on the way. Has anybody experienced a 3+ minute wait time? Obviously, that wait isn't suitable for a busy store.

A few follow up questions.

1. How do I know which wallet software is capable of creating a public key for every new transaction?
2. Assuming the storefront has a tablet at checkout, what app/software should a business like that use?
3. Is it recommended for the business to sell a % of BTC into USD immediately to protect their capital from the volatility of Bitcoin? (I suppose this depends on the market climate, but if the store owner doesn't care/have time to keep an eye on what the market is doing I'm sure the selloff to USD would be his/her preferred plan)

Thank you for taking time!