any advise on hotels in nurnberg and wittenberg?

You did not mention when you would be traveling. Nürnberg is popular trade fair town. It has many hotels and they tend to fill, with much higher prices, when there is an event scheduled. I would check a hotel referral website to see what the going rates are when you will be visiting.

https://www.hrs.com/?dynStartDate=1&singleRooms=0&doubleRooms=1&adults=2&customerid=410736001&extcmp=PS-uk-7631-GoogleUK_Desktop_Brand&HBX_PK=Hrs%20Com&HBX_OU=50

Among the chains we liked the Motel One.

We also liked the Art and Business hotel when the going rates are not high.

https://www.art-business-hotel.com/home-en/

Check out Hotel Marienbad. Had a nice stay there a few years ago.

I'll be staying at Hotel Victoria near Nuremberg station and have read good reviews. The review on this forum, although a bit older, gives nice information; the newer ones on TripAdvisor also spoke highly of it. I've had very pleasant booking interactions with the staff.

Back in 2012 we arrived in Nurnberg without reservations and had to check a few hotels before we found one with available rooms. We stayed at the Durer hotel and it was fine. It has its own parking garage.

We stayed three nights in Nuremberg three years ago during early December at the Drei Raben hotel and loved it! /It was very convenient to the Christmas Market as well as to the tram lines. Not a very long walk from the train station. The staff was very helpful and the hotel offers a complimentary "happy hour" each afternoon. A business class hotel so a little more pricey but well worth the money.