I installed Electrum and created a wallet there. All I know is the seed generated. I don't know private keys from the Bitcoin addresses it manages for me. And I don't see an option to get them from there. So, the question is how safe this system is? Won't I lose my bitcoins one day?
If you have save your seed & export your all private key then you are safe almost. But you should keep safe your data on multiple places. Because in case if lost your saved data then there is risk of lose your fund as well. Another most important thing is during update of your electrum wallet. Few days back we have seen multiple case that hacker successfully hacked few wallet by malware. During update they got control of wallet and in a result hackers moved fund into their address. That's why you should always be careful during update your wallet. It should redirect original website.