DH and I are headed for a multi city/country adventure in March 2019. We booked a Business class RT using AA points, we will be landing in FRA and I need to schedule a flight to Berlin. How much time should I allow for customs and immigration? We will be booking, at least, business class tickets to Berlin. In addition, we would really like to do rail from Budapest back to FRA-seems like the landscape is beautiful-for this one I would appreciate opinions on rail versus air. We will be staying at an airport hotel the night before our departure so little to worry about with time. Sorry if my abbreviations or lack thereof offends, I am so new that I don't know the lingo of flyertalk. I really appreciate any advice or suggestions. Thanks!