keep moving and when he attacks hit him with a bow not sword!

run and hit thats how i beat him but use a bow

The Gnar has good attacks...
He can damage you a lot with one hit...
The key here is to stay away from him and shoot him with long-ranged weapons...

On your first battle with Gnar, go behind the true Rose until he's behind you...
Go away from him and he should be stuck behind it...
Attack him and he should run away...

On the second battle, I suggest you buy the Bless Scroll first from Eric the Wise in the
docks to aid you (any healing scrolls will do)...
And then just do the hit-and-run technique...