blockchain – Bitcoin stuck in the bitcoin core

Aware of the fact that Bitcoin Core has to sync 800gb of data before displaying my coins, I transferred some money into a wallet created with the app. Now my money is stuck. The files are too many for my system.
I tried to retrieve my wallet through a public / private key, but it doesn't work on blockchain (it says my wallet is empty) or electrum. Also, the transaction with which I received my money cannot be found with insight.bitpay, but I can find it on Blockchain.
I can't understand I have my public and private wallet key, is it possible that I lose my currency?