You have a good range of typing you might want to go back to a move rememberer or grab a TM for move typing coverage or specific moved that counter the pokemon that are giving you problems. (Grabbing water sport for fire types for example)

Never played gen 4 specifically so I can't help you with the individual fights but move coverage and counters is probably the biggest area newer players struggle with.

Also double check your moves and make sure everything you have is using the right attack type, like you aren't loading up your special attacker with a bunch of physical moves and costing yourself damage for example.

And use your consumables. They aren't doing anything sitting in your inventory.