Here are some possible ways to ask and respond to these questions:
Are we having class today?
Can you confirm if we have class scheduled for today?
Is our class still on for today?
Are there any changes to today's class time?
Has there been any update or change to the scheduled time for today's class?
Do we need to adjust our class time for today?
How to agree on a time to have class, other than “sure”?
That time works for me.
I am available at that time.
Yes, let's plan for that time.
How to say I'm okay with having class at a particular time, like “6pm is fine”.
6pm works for me.
I'm available at 6pm.
Yes, I'm okay with having class at 6pm.