Student or Learner
It's lunch time and I went home to take a break.
When time is almost up, I went out and tell my son,
"I have to go out now."
"I have to go to working now."
"I have to go out now and back to work."
Are they colloquial?
#2 is wrong.
The others are possible, but I'd say 'I have to go back to work now'.