Hello,
It is not possible to change any values in Clash of Clans via cheat engine. Simply because cheat engine can only change variables that are client side. So if you would try to change the ingame currency in Clash of Clans, let's say, from 10 Gems to 500 Gems, you may would see it but you would not be able to use them since only the server of Clash of Clans can change those values.
You would actually need to hack into the Clash of Clans server so that you would be able to change the values. but that is first off not legal and secondly pretty hard to do.
Best regards,
Sebastian Schuster