am trying to purches for an app but all i get back is your purches could not be completed

Hi there, Pobi96!
Thanks for reaching out to the Apple Support Communities! It sounds like you are having issues with making purchases on your iPhone and I am happy to help! I recommend you check out this article with steps to follow If your payment method is declined, or you have a billing issue with a previous purchase in the iTunes Store. This article will give you the best steps to take for issues with making purchases with your iPhone.
Cheers!