Question about safety: is it safe to give our private keys to unknown wallet like Electron Cash? Maybe imnediately after giving our keys to BCC wallet, we have to send our BTC to another wallet to guarantee safety of our Bitcoins?
No
, it is unsafe, that is why send your BTC to another wallet before you dare to use any unknown wallet, and send all the BCC you obtain to another address (maybe on exchange) immediately after you gave it the keys.