Quote from: nejel on August 06, 2017, 10:21:18 AM

Thanks, I've gone a little bit further in the process but another problem occurred. I can't sign transaction because offline wallet restored from private key is related to uncompressed address but transaction with compressed. What can I do about it?

You can convert the address from a compressed key to an uncompressed one, vice versa.

AFAIK, you shouldn't encounter any problems using a uncompressed key in the client. Go to your offline instance of Electrum and go to the address tab. Check your address against the one on your online computer. If they don't match, you have to press Wallet>Import address and paste the address that is shown on your offline computer.