Hello,
For the first time i moved now from blockchain.info to some offline wallet bitcoincore.
I have a few questions now,
1) i did encrypt my wallet using some password so it´s safe right?
2) i did a backup but have only 1 file called wallet.dat (is this all i need as backup)
1)If you did not expose the private key before encrypting (Usually safe if you do it offline on a clean computer). Or get your encryption password keylogged. Then yes.
2)Yes. Try restoring it on another computer to get the hang of it.