Topic: Pokemon y online battle help

Well im just looking for some tips because i have only won twice out of like 15 times of battling online
My team:
Greninja-ice beam, extrasensory, waterfall, surf
Arcanine-heat wave, flare blitz, crunch, strength
Garchomop-dragon claw, draco meteor, dragon rush, rock smash
Noivern-dragon claw, draco meteor, air slash, fly
Venusaur-sludge bomb, petal blizzard, sleep powder, cut
Umbreon- bite, psychic, shadow ball, recovery
Items:
Greninja-leftovers, arcanine-N/A, garchomp-garchompite, noivern-dragon fang, umbreon-dark glasses, venusaur-venusaurite
This is what my team in so maybe some friendly tips would really be helpful
Also add me friend code- 2363-5662-2180

Oh boy, you really do need help.

First things first, what's your Pokémon's nature?

Greninja-sassy
Arcanine-bold
Garchomp-sassy
Venusaur-bashful
Umbreon-serious
Noivern-rash

These natures and move sets are better for your Pokémon:
Greninja - Timid
Arcanine - Adamant; Close Combat, ExtremeSpeed, Flare Blitz, Church/Wild Charge (provides good coverage)
Garchomp - Adamant or Jolly; Outrage, Stone Edge, Fire Fang, Earthquake (pure offensive)
Venusaur - Modest; Growth, Sludge Bomb. Giga Drain, Hidden Power Fire (The trick is to have Ninetales use its Drought and with Venusaur's Chlorophyll, it can out speed any Pokémon)
Umbreon - Calm; Wish, Toxic, Protect, Foul Play (serious is still good, but calm is better because of Umbreon's high SpD which can annoy your opponent)
Noivern - Timid

The last 2 doing some research right now. Any Questions?

So for the natures how would i change those?

^Natures can't be change once their set (unless through hacking), the only way is to breed new Pokémon.

Ok thanks so much for your help hopefully all your tils will help me get better

^No problem.

Also, are you using super training?