1. I know that transaction can't be canceled or removed
2. When I send transaction of 0,5 btc it was not added to blockchain, so just my core wallet show that it was send. So this trasaction wa not confirmed by any miners.
3. To take this coins back to the balance of bitcoin core I remove wallet.dat and restart my bitcoin core. Bitcoin core reated new wallet.dat and I added private key from previous bitcoin wallet.
4. But when integration was dane, bitcoin core was send this transaction once more but before this transaction core automatically send 0,12 btc to 1K1xArpDHtkmPpg9bNLgpBxTqw8xw3SDPE, which I do not know (I or somebody else never use this address). Maybe this address is the new addres of my bitcoin core and wallet made this transaction to confirm the low fee transaction.
5. I know that these transactions is already confirmed
6. The question is what is this addres? Why bitcoin core made this transaction AUTOMATICALLY to 1K1xArpDHtkmPpg9bNLgpBxTqw8xw3SDPE? And how to take my 0,12 btc back, if it possible?
Well, the transaction where you sent 0.5btc to 196y4iA7kZHEHVY9NmZqtTRbD76WWV43Cf was confirmed. In that same transaction 0.124 went to 1K1xArpDHtkmPpg9bNLgpBxTqw8xw3SDPE . Internally core has a bunch of addresses it uses to send residual balances to, when you send it's actually picking various transactions that were sent to you and they have to add up to the amount your sending elsewhere, or greater, the "greater" part is what gets sent back to your own internal addresses. .... anything in those will show up in your balance however. (you can see this in core if you choose coin control when sending) .
My guess is it's one of those if you didn't explicitly send to that address. When you made a new wallet, you didn't import all the keys, is my guess. Do you have your old wallet.dat? Did you back it up immediately before making a new wallet.dat and importing old keys, ie, did you import ALL the keys from your old wallet, there's many more than just keys for receiving addresses that show up in core. YOu can view all of them in the console or dump them all from the console as well. If your sure it's not showing in your final balance, it's in the old wallet.dat, you need to export ALL the keys from there. A simple test would be to just put your old wallet.dat back in place (moving your current one to a safe name/place) and restart core. you should see your 0.124 then. Then export ALL your keys, switch your wallet.dat's again and import them into your new wallet.