some advice pls

Halo has always been a game that takes skill to get kills rather than just being able to aim at the enemies. You're definitely not bad at the game, its just that Halo's gameplay is generally more complex than in other shooters. Even worse, ODST is one of the hardest Halo games. But if you get good at this one, you'll probably be good at the rest of them.

General tactics for ODST:

1. To kill grunts (the little guys with the squeaky voices with the big tanks on their back), use the pistol or the carbine and try to get a headshot. One headshot to a grunt is a one hit kill on all difficulties.

2. To kill Jackals (the fast bird like enemies with the round energy shields), shoot through the holes on the side of their shields. This will stun them a bit and they will expose themselves for a few seconds. Either finish them with an automatic weapon or use the pistol or carbine to finish them with a headshot. Another tactic is to use a plasma weapon to simply destroy their shield.

3. For Brutes (the big monkey guys), pick up a plasma pistol and hit them with a charged shot. This will drop their shields completely. After doing this, a single headshot from the pistol or carbine will finish them off.

4. For Hunters (massive armored blue enemy with the big laser gun), you'll need to maneuver behind them and shoot them in the exposed orange area on their backs.

Those are just a few general tips for how to dispatch some of the game's enemies. If you need help with anything specific, feel free to ask.

By the way, there's a new Halo game out called Halo Reach. You should probably pick that up if you like ODST a lot.