Hi!
Can I send btc from paper wallet offline (I mean sign tx)? Or I have to connect to internet?
If I use Electrum by seed (offline computer) I can get a xpub key, then I can put it into online computer Electrum and sign tx. But when I import 1 private key into Electrum (from paper wallet) I can't get xpub key.
You can sign tx offline, but you need to have the Internet in order to broadcast it to the network, you can use tools like:
https://blockchain.info/pushtx or
https://insight.bitpay.com/tx/send.