Here are the suggested completions for the sentences:

1. It is over two years since they left their homeland. (They haven't **been back**.)
2. "How many cars are there in front of your house, Mai?" I said (I asked **how many cars**).
3. No one introduced me to newcomers in the festival. (I **wasn’t introduced**.)
4. The food was too bad for the children to eat. (The food was so **bad that**...)
5. It’s no use persuading her to join in that activity. (There is no **point in**...)

Feel free to ask if you need further clarification!