I played the first one through and loved it. I'm now playing Witcher 2 and loving it as well.
If your concern is the plot and back-story, I think you'll do fine just reading the plot summary on Wiki
As far as importing a save game, it carries over a little bit of money and gear, but nothing that gives a huge advantage. You'll have earned more money and better gear in a few hours anyway.
The biggest issue I can think of is in understanding the mindset of the character, the game, and the world. The Witchers are powerful warriors like you'd find in other games, but that's not what makes them interesting/unique. Their specialties are knowledge of the many exotic monsters and their alchemy with potions (and traps and bombs in this case).
Reading/researching about creatures would be optional codex/lore in another game, but here it is part of the quests themselves. Potions, bombs, traps would be optional consumables in another game - and I personally rarely use them - but here they're critical.
Many people are struck by the difficulty of the game, and it's usually because they're trying to sword-fight their way through everything. If you really make use of the traps, bombs, potions, oils, etc. you should do just fine.
Lastly, understand that the character Geralt is not trying to be a heroic soldier. Unlike in comparable RPGs, you're neither a great hero nor villain, just something like a tough exterminator travelling from village to village cleaning up their monster infestations. Getting caught up in politics and wars is anathema to the cynical Witcher who just wants to be on his way to the next job.
As sjohnston stated, if you manage to stun an opponent, you will be able to perform a so-called finisher move on him.
The probability of landing a finisher move depends on the chance of causing a critical effect, in this case, stunning.
You can view your chances of causing critical effects in the character panel (enter meditation and select "Character" from the radial menu)
The odds can be raised by getting or improving the appropriate skills, acquiring new mutations, drinking potions and using oils.
Best Answer
Make sure that you keep running down. Don't let go of that key.
The game is prompting you to press the right mouse button to dodge into cover from the dragon's fire. You'll notice the icon appear near the bottom of the screen; press it as soon as you can so you don't die, then continue running.