Another common mistake in English.

What do you do?

Spanish

speaker: I'm having breakfast.

But the question is asking what you do as a profession or if you are a student etc.

The Spanish speaker is answering a different question like what are you doing right now?

Then you can answer I'm having breakfast.

For example, what do you do? or what do you do for a living?

I'm an accountant.

What are you doing right now?

I'm having breakfast.