I must be missing something. Every combat I get killed really quickly. What's wrong?
Stick to ranged weapons like bows and fight from a distance. Don't fight with a lot of units at once.
Also you won't be able to match many enemies in the beginning. Try to stay in the northern part of the map at first until you level up a bit.
That is some solid advice! Ranged weapons such as bows and arrows or clever combinations of magic cards (your magic stats permitting) will be a lot better than melee. Melee combat is clunky and not very well balanced in the early game; it's not until later that you become a killing machine with huge Strength and health, and massive amounts of armour.
There's a lot of cool skills to invest points in, my favourites being things like mounted combat and bashing people around the head with a torch, but they're not all that practical until you get more experience or are at a level where you can increase their effectiveness. If you've not won a combat yet, I'll assume you're not far into the game.
You'll want to stick to Groms and wolves to begin with, moving onto skeletons, boars, bears and wyverns later. The difficulty will leap depending on what enemies you're facing so be careful. I know it's glorified pest control, but you will come across and be able to have a fair fight with much more interesting enemies later. ^^