My bicycle had a blowout  (OR 'a flat tyre')

I always go to my part time job by bicycle. Today, after my part time job had finished, I think I get thought about going home, but my bicycle had a blowout. (OR 'a flat tyre')

'had' - Use the PAST PERFECT when you want to show that something happened before something else in the past.

I was sad and angry, and tomorrow, I've gotta got to go to my part time job in the morning. But I haven't got time to repair my bicycle. So, I think I borrow my mother's bicycle.

'Gotta' is only really used when speaking or in very casual texts like song lyrics or text messages.