Private keys are your access to your bitcoins. Who ever knows your private keys(also known as seed) controls your bitcoins. It is not advised to share your private key with anyone. Also you should not keep it online, rather make a paper wallet or buy a hardware wallet like Nano-S or Trezor. Stay safe!
Thank you for your information .
And what about Electrum , is that safe to use that ?
What is watch only wallet ?
Second question : Can I create and use a password to access my wallet in Electrum ?
Watch only is same as read only. You'll be able to see all the addresses within the wallet but unable to spend those bitcoins.
And yes you can. Electrum supports pass protection. You need the pass to be able to send BTC ... without pass it's just read only (watch only) wallet
Thank you for info. And please can you give some more info about watch only option .
And , I have second question : even if I use password protection in Electrum wallet , then someone knowing my private key can steal my BTC even if that person does not know the password ?
Watch wallet is used to monitor balances and incoming payments.
You can use this wallet on unsafe devices like shared computer in your job or your friends device (no reason to do that, just example) and still be safe.
Anybody who get access to the wallet will see all addresses and their balances but would not be able to spend those BTC.
And Yes.
Person knowing your private key is able to send out bitcoins stored in the respective address (not entire wallet).
Wallet is just tool to help you manage multiple addresses (each address has it's own private key).
The password simply protects entire wallet but once the prv. key is disclosed you should never use that address.
Some example.
In past I had very small amout BTC in one of my addresses and wanted to give them to my friend. Instead sending them ( which would cost half of the balance on fees) I rather decide to give him the private key and he imported this address to his wallet. So now we both have controll over this address (and can spend those BTC).
