could someone tell me what is the minimum amount sendable in BTC with electrum
It's 546 satoshi or 0.00000546 BTC, there's no other such rule of sending minimum BTC with electrum, nor any other wallet other than sending BTC from centralize services like exchanges. They may have minimum amount to send.
Electrum wallet is totally controled by you, hence, you can do whatever you want. Make sure you are using authentic source to download the wallet and verify the signature.