It all should have been explained in the tutorial sections of the introductory chapter.
The basics:
-In combat, to continue a combo you have to click at the moment Geralt finishes the first move - this is signalised by sound and graphics (watch the tip of the sword for sparks) and, on the lower difficulty levels, by the change of the icon. This means that the combat is not button-spamming, but more of a rhythm game. It's worth reducing the difficulty for a while to get into the rhythm. Also remember that there are 3 fencing styles - fast, strong, and group designed for different opponents, as well as two swords.
-How you look around depends on the camera you choose. The options are high isometric (F1), low isometric (F2), and over the shoulder (F3, also F, and G to change/flip the camera). Also it's worth noting that holding the Alt key will highlight and objects.
More info can be found in the tutorial tooltips in-game and in the manual.
Have fun!