Learn to pace yourself. Remember that you don't have to kill all zombies. Shoot them in the leg and make a run for it. Go for headshots, then kick them.

I'm currently going up against Krauser in Professional mode and bloody hell... The cheating sonova refuses to DIIIIEEEEE.

That is quite a healthy selection of ammo you have there. I mean, that's a LOT of shotgun shells right there.

More tips:
Get a TMP... Its worth the money. Plus its the only gun in the game that doesn't have a variant.
Only use the broken butterfly for boss fights as it pretty much overkills all zombies
Get the stock for the Red9
The scope for the sniper rifle is a waste of money... You don't need the extra distance

Remember that the ammo placement in the game is often like this:
Lots of items scattered around where you can stock up on ammo, followed by an area with hardly any items and lots of enemies.

Here's a quick tip: You know those zombies that have their heads explode to reveal those tentacly things? A flash grenade kills it instantly.

You do realize that since the beginning of time beginning of the series, Biohazard was the original name of the Resident Evil games? Its just that Resident Evil is the name of the game outside of Asia.

Now, this would make for a perfect case for the "graphics vs gameplay" argument that gets thrown around a lot here since the gameplay is pretty damned good despite the craptastic graphics.