I bought Minecraft PE on my phone. Then I changed the device. I logged in with the same account in the Playstore. But with Minecraft I have to pay 7.99 euro again. How do I get that, that I do not have to pay again?
You have to sign up with the email you used to buy it. You only bought it for the account so it's only marked as bought, so check it out again if you really use it.
If that still does not work and you have really taken the same account, look for the bill and report to support.