http://reiseauskunft… Use Frankfurt Flughafen (airport train station) as your departure. It’s 4 1/2 to 5 hours with 3 or 4 trains every hour, so it will be very easy. The only direct train from the airport station is at 17:03, but it actually takes longer than the routes that involve a connection. If you take an ICE train, the connection at Hannover, Leipzig or wherever will be fast and very easy (probably just walk across the platform to the waiting train). Connecting from S-bahn (commuter light rail/subway) to ICE in Frankfurt will be a little more complicated, but certainly doable.