"I have to go for work soon.."
They are confusing two different expressions:
"I have to go to work soon.."
"I have to leave for work soon.."
In full form, the sentences would be:
"I have to go to my place of work soon.."
A person 'goes to' or 'goes away from' - we are talking about 'travelling', and travelling 'to' somewhere.
"I have to leave soon, bound(=heading toward somewhere) for my place of work."
Here, we are talking about the destination, and we 'leave for', 'depart for' somewhere.