1: This supermarket is less expensive than the one across the street
2: At Mid-Autumn Festival, children carry beautiful lanterns so it's a memorable childhood expensive
3: Mai really likes hanging out with a friend
4: My sister does yoga more frequently than me
5: You don't have to change the dates of our trip

 1. This supermarket isn't as expensive as the one across the street (less)

→ This supermarket is less expensive than the one cross the stree

2. At Mid - Autumn Festival , children carry beautiful lanterns . It's a memorable childhood expensive (so) 

→ At Mid - Autumn Festival , children carry beautiful lanterns, so it's a memorable childhood expensive

3 . Mai is really hooked on hanging out with friend

→ Mai really likes hanging out with a friend

4 . I do yoga three time a week , but my sister does it almost every day ( frequently)

→ My sister does yoga more frequently than me

5 . It's not necessary to change the dates of our trip ( have to )

→ You don't have to change the dates of our trip