I was working at the xyz machine, Or I was working in the xyz machine.
If you are standing or sitting by the machine, use at. If you are talking about something like a workstation, I would use on.
And, I have enough leave on me, Or I have enough leave for me.
I have enough left for me.
Also, I'm in bus or I'm at bus.
I would say on the bus.
Student or Learner