1. The Great Wall of China is the world’s longer structure.

longer => longest

2. Traveling by tram is most convenient than traveling by car in this city.

most => more

3. You must taking off your shoes before entering this room.

taking => take (Sau must + V_infi)

4. Do you think there is another mountain highest than Mount Everest?

highest => higher

5. Ha Long Bay is the more beautiful natural wonder of Viet Nam.

more => most

6. The scenery of the Amazon rainforest in your pictures looks incredibly.

incredibly => incredible 

7. In my opinion, foreign tourists visit Hoi An just to its ancient houses.

to => for

8. Missouri is longer river in the USA, but it is shorter than the Amazon.

longer => the longest

9. Meghalaya in India has more rainy or wettest weather in the world.

more => most

10. Lang Son is one of the coldest province in North Viet Nam.

province => provinces

1. longer -> longest

2. most convenient -> more convenient

3. taking -> take

4 highest -> higher

5. more -> most 

6. incredibly -> incredible

7.its-> (bỏ)

8. longer-> the longest

9. or -> and

10. North-> Northern