We got some native speakers' help for it.
We made 5 groups with all foreigners and students, and TIA directors joined in the groups and they had conversations together.
In each groups the foreigners pretended as a school teacher , host father , shop master or others.
Each 2 students were rotating around groups for conversation training.
We do thank you to Mary Aruga, Anthony Gordon, Shaneece Johnson, Alex Theeack, Nigel Hay.