Is it ok to purchase a car before bankruptcy or after bankruptcy . inquiring about chapter 13 ?

Well if you purchase the car before chapter 13, I think you would have no more notes to pay. But chapter 13 prefer you not to purchase any thing after filling.

Before you can keep it and get the notes down

You have to have the loan for at least 1 or 2 yrs before you file

I would say before so you could claim the property before you finalize the case, but I would definitely ask the lawyers at the firm first just to be sure.