Please check my sentences gramatically (7.11)

I volunteer for elementary school students as their english teacher.
I think the students were active in my class because I gave out candy.
I gave candy to children who answered my questions correctly.

Yesterday was the first day that they started wakeboarding.
They fell down in the  water.
It took a long time to meet them.
I want to meet them as much as possible.
Wakeboarding is a good bridge to make us often meet.

I'm practicing tricks like jumping and switching.

Agency will give us volume 1 to study again because there were a few units that we didn't study.

My flight is schedule to take off at 7am.
The runway was frozen because of heavy snow.
The staffs istrying to melt the frozen road.
It will take 2 hours.

How about getting another person to attend the meeting.

Can I postpone the meeting time to the day after my arrival?
I cannot get there until tomorrow.
Let me know what is the best alternative.

I don't like that the schedule has suddenly changed.