Originally Posted by NewbieRunner

You have not said where you will be arriving from but there were two UA flights arriving at 11:50am today.

UA74 EWR-FRA arrived a little early but was a bus arrival.
UA932 IAD-FRA arrived late at gate Z20.
Your flight to DUS is likely to depart from an A gate.

If your United flight arrives on time or early you have a chance of making the connection to your DUS flight, but as you know you will have to go through passport control and it will be very tight. Assuming you are on one ticket you may have to be prepared to be put on the next flight to DUS at 5:00pm.

If you arrive at a Z gate check if passport control into Schengen near gate Z25 is open as it may have a shorter queue than passport control near Z11. If you arrive by bus you will have to follow the signs.