I am arriving in Frankfurt on a Saturday morning on an overnight flight in early November and have a six hour layer before my conncecting flight to Africa. Do I have enough time to go into Frankfurt? What recommendations do you have for things to see that would be open then or any place to get a coffee and pastry? How far ahead of my flight do you think I would need to be back? How long will it take to get into Frankfurt from the airport? Thanks for any help you can provide.
If your luggage is checked on to Africa, you don't have to worry about retrieving it and rechecking it. Nevertheless, it takes about 15 minutes to get into the Frankfurt Hbf and another 15 minutes to get back. And you should be back 2 hours before, so that leaves you with 2½ in Frankfurt. I'm not sure there is anything worth seeing in Frankfurt in only 2 hours. Don't risk it; stay at the airport.
If I were you, I'd check out the amenities available in the airport. I don't know about Frankfurt specifically, but many airports have showers FRA, being one of the major world hubs, should be well-equipped.. Six hours gives you enough time to get cleaned up and to have a leisurely coffee and whatever. Be kind to yourself and don't push the envelope before you even start your trip.
It is difficult to overstate how big this airport is. It could, possibly, take 20 minutes just to walk to the non-secure area and look for the train station. It would seem that you are also making a choice between a transit lounge and waiting in line for Non-EU Passport screening, which could take 20 minutes too. (However, if Africa is in a different terminal, you'll probably have to do immigration anyway.) Your hope is not realistic.