Here are the correct forms of the words to complete the sentences:

1. Paying respect to people of **seniority** is a traditional in Viet Nam. (SENIOR)
2. The Lion Dance is usually performed at Mid-Autumn Festival, where the dancers **skillfully** dance to drum music. (SKILL)
3. There has been a sharp **increase** in the number of vehicles in Ha Noi. (INCREASE)
4. Teenagers nowadays **publicly** share their feelings and emotions by posting them on Facebook. (PUBLIC)
5. Viet Nam had experienced decades of fighting for freedom before the country became totally **independent**. (INDEPENDENCE)
6. She often **entertains** her children by telling them stories before they go to bed. (ENTERTAINMENT)
7. English is such a **nation**al language that learning it well brings students great advantages. (NATION)
8. In the first place, because English is often included in learning programs, a good understanding helps to meet a compulsory requirement in many schools and universities. (KNOW)
9. Another benefit of learning English lies in exploring more subjects and **information**. (INFORM)
10. There are a huge number of materials written in English, so this language **enables** me to gain further knowledge about all aspects of life. (ABLE)
11. English guarantees a high-paid job since most companies prefer employees with English ability to **communicate** with foreigners when necessary. (COMMUNICATION)

For the second section:

1. The foreign visitor was really impressed by the **breathtaking** views in the mountainous areas of Vietnam. (BREATH)
2. I wish I could join the tour to Korea. The tour is too **affordable** for me. I need to save more money for it. (AFFORD)
3. Old people prefer to buy **packed** tours for their travel because everything is well-prepared by travel agencies. (PACK)