Electrum is a Non-custodial wallet where you can safely hold your bitcoin because when you have done the creation a wallet thete you got a private key. and that key will help you to access your bitcoin and that key is not possible to hack by any hackers.
It is not impossible for your assets to be hacked in any wallet, including electrum, there are wallets that are safer than others, but you cannot say that you are 100% secure and your funds cannot be hacked. Mind you that Electrum is an online wallet, and if you use an online wallet, there is a higher possibility that you could be hacked because the device that you keep your assets is connected to the internet.
for this you have to take help of a centralized exchange like binance then transfer your btc to Binance and sell it on p2p
You can trade your assets in a centralized exchange, but i want to point out that if you wat to trade peer to peer, you cannot do that in a centralized exchange, but in a decentralized exchange.