Can i buy apple care from Iphone if my Iphone 14 pro max is bought in another shop?

Yes, you can add AppleCare+ within 60 days of purchase of a new iPhone from an authorized reseller. See→AppleCare Products - iPhone - Apple and click Buy Now at the top right on the page.

As long as that shop you bought the iPhone from is in the same country and you live and will use the phone in that country, yes, you can add AppleCare+. You can't for example, buy an iPhone in the US and then add AppleCare+ to it in France.