Just a litle addition, if you first play on easy to get all gold bonuses. You will stil have them on Hard mode (not all at once but on the lvls you should otherwise have gotten them).
Next to that: block, hit, block, hit, etc. Don't try to just keep on hitting or you will die. The best thing to do is block the first attack than quickly hit him, now block in time again and hit. Keep on doing this and you will notice it is allot easier to complete the game. Try to go for combo's aswell becaus they will die quicker.
Also when about 2 or 3 enemies attack you at the same time try to go back into a door opening and block the first getting in, the ones behind him will start hitting him. So they will kill each other.
On some places your could just sprint to the next checkpoint while dodging attacks. Like in the museum after you jump from a ledge.
And if you get a gun make sure to make a headshot, becaus headshot = 1 hit kill.