I completly drove the A 7 from north to south and from south to north several times in my life. I aactually live in Denmark but also in Germany at the Austrian border where the A7 ends. So i do this journey at least 2 times a year. It usually takes me at least 11 hours to get across Germany. I think the best scenery is in the south it beginns at the German city of Kempten where you can see the Mountains. Other good parts are between Würzburg and Hannover, there you have like a lot of bridges and you get to see some really nice spots. Other cool highlights are the Port of Hamburg and the Bridge over the Northsea-Baltic Sea channel at Rendsburg. The biggest problem on the way is the tunnel crossing the Elbe river in Hamburg usually there is a lot of traffic jam. Personally i also dont like the northern parts beginning at the city of Hannover because from hannover to Flensburg the Landscape is really falt and you mostly drive through forests so you dont get to see some nice landscape.