I read about Electrum and installed it, but I don't really understand how I can put the money there... because you can't buy directly with euros/dollars. Can anyone give me some insight?
You should buy bitcoin in exchanges and the withdraw the fund to one of addresses generated by electrum.
You can also buy bitcoin from someone peer to peer and ask them to send the fund to your address.
In general, I would like someone to tell me a wallet to use that is safe and easy to use so I don't get so lost with so many that exist.
Electrum is open-source, its code has been reviewed by many people is safe.
Just take note that any online device is always prone to hacking. It's always possible that your device is infected with a malware and your wallet is compromised.
If you want your wallet to be completely secure, you should run electrum on an air-gapped device.