I'm not familiar with kryptonia.

In my experience, the easiest way to accomplish what you want to do is to use an exchange that lists SBD or Steem (like Binance) or BlockTrades.

RE: Using BlockTrades

The process outlined in the below post is actually the reverse of what you want to do.

Just take what I did and do it in reverse; meaning, send your BTC or any of the other supported cryptos to BlockTrades and they do the rest (convert your cryptos into SBD or Steem and load them into your Steem wallet).

See: https://steemit.com/steemit/@jaichai/ijch-why-and-how-i-sent-steem-for-the-first-time-objective-cash-out-in-foreign-fiat

Note:

BlockTrades doesn't usually work with exchange wallets, so you need to send your cryptos from a private wallet.

And for Buddha's sake, even though BlockTrades is very forgiving and responsive when users screw up, do yourself a favor, make sure you review your whole order at least 3X before pressing that "Send" key.

Namaste, JaiChai