That’s plenty of time.

Trains run every 15 minutes and take less than 10 to get to the main station. The ticket machines in the train station hall take cards. There are also lockers in the train station at the airport so that might be more convenient. See here for detailed info on lockers.

Most places accept credit cards nowadays, Switzerland has made progress in that regard.

With a business class ticket you should aim to be back at the airport 45 minutes before departure as the priority security lane rarely takes more than 2 minutes.

Old town is a bit further but it’s nice if you have already seen the lake and fountain. Try https://www.lesarmures.ch/en/restaurant/ or https://www.cafepapon.ch (reservation highly recommended around lunchtime)