is the only backup I have just the data in wallet.dat? is this safe?
I do not advise you to extract the private key, a.k.a master private key, as wallet.dat allows you to encrypt your private key with a password, and the stronger and unique it is, the more difficult to hack your wallet.
bitcoincore wallet is not a good option for beginners so why not use any SPV wallet like
https://electrum.org or
https://sparrowwallet.com where you get your 12 words wallet seed which can be easily stored offline.
Yes, for now I have used electrum because it is easier. But because Bitcoin Core is also one of the popular Bitcoin wallets, I also want to have it.
I'm also not interested in making modifications or other things, I prefer to use a wallet with standard functions and the most important thing is that it's safe. Thank you for the advice you gave