I recognise some of the places in the pictures. Must have been some tour.
Yes, the north of Poland is more agricultural and flat but that doesn't mean there is less to see. Leba (pronounced Weba, funny L) is a popular holiday resort with miles of good beaches. The old Nazi test centre for the rockets is now a museum. You'll need a bicycle which you can hire. Visit the dunes while you are there. The road there looks like it can be entertaining on a bike.
The tri cities of Gdansk, Sopot and Gdynia. Gdansk has the old part of the city. A major port in the Amber route of ages ago and a walled city of which the remains can still be seen. Lots of impressive old buildings and a rich history. The ruins of the fort on the hill gives a panoramic view. Westerplatte is only a boat trip out to the military fort that was the scene of the first battle in WW2. Sopot is where the rich people hang out. Good beach and it caters for entertainment. Pleasant place to visit. Gydinia has the Aquarium and a ferry that will take you to Hel which is a peninsula in the bay. You may be able to spot a submarine in the bay.
Then there is Malbork just to the south, the biggest castle in the world and build by the Teutonic nights. A tour by one of the guides is recommended but pricey. When we visited the restoration was still ongoing after the destruction in WW2 by the Russians.
Hitler's Wolf Lair is to the east of Ketrzyn. I have not visited but the plan is to combine a trip there with a visit to the family.
Enjoy the tour. The people are really hospitable and I'm sure you will have had your fill of vodka.