Multiple Questions

Hello everyone,

This is my first post here. I have been wondering about how to write questions for a long time and when someone emailed me with a couple of questions I had to look for someone to ask.

The question in the email was "When does he come back is it Monday?". The problem with this is that it is actually two questions, so should he have written this: "When does he come back? Is it Monday?". Or is the only thing that is missing here a comma? When does he come back, is it Monday?

What is the correct way to write this?

Thanks,

Sachin