Student or Learner
Is it ok to say "Sorry, I cannot come, I made appointment with someone before you." or do I have to say "I made appointment with someone before I made appointment with you". Which is correct?
No, don't say it that way.
It sounds like they want to meet at 3, but you have an appointment at 2.
Say "I'm sorry, I can't come. I have a prior engagement."
That means the other appointment existed before the request from one you've received from the speaker.