Today I have meetings all day, which I did not know what time it is finished. But I will wait for your message and will send you a message after the meeting finished.
Today I have a meeting all day, which I did not know how to complete?, but I will wait for your messages, and send messages to you again after the meeting.
Today I have a meeting that day, and I don't know that will be completed within a few hours, but I will be waiting for your message and will send a message to you again after you have finished meeting.