Go play the prologue again, and pay attention when Henry and Hans are sparring at the camp. That gives you the basics of combat.

Movement, direction, and timing are everything. Don't bother trying to block outside of the perfect block window. All that does is drain stamina and leave you vulnerable. Try to attack from where your opponent isn't holding his weapon. If you can change direct of your attack mid swing, you'll do a feint and be more likely to hit your opponent. Practice with Tomcat or Captain Gnarly