1. Where do elderly people travel by bike?

In Germany, I often see people, even people *over eighty years old* traveling by bike.

Здесь ключевое слова over eighty years old.

2. Is it strenuous to travel by bike in Northern Germany?

Ответ: No

Так как у Northern Germany дороги плоские. (it's less strenuous).

3. What is he going to do in England in summer?

He's going to cycle more instead of taking a bus.

4. What does the landscape of Sheffield differ with?

Because, there are 7 hills and this would be challenging to go up using just a bike.

5. Why should you be careful in Oldenburg?

Why? Because, in Oldenburg there are more bikes than people. Which make the city as cyclist zone. The only thing that you should be careful of a cyclist who would hit you accidentally.