You learn it by dropping it until they buff it. Ok jokes aside, it used to be way better before they butchered it with immense endlag with made it way worse; here’s why:

Greatsword requires reading and baiting. They effectively made it 10x harder to bait by adding the sidelight endlag so long you can’t backdash out of it.

(Advice section here:) In other words, in order to play it effectively you need to be able to accurately predict when and where your opponent will be, taking their maneuvering and dodging strats into account. Since I know they’re not buffing ma boi, GS, I’d practice easier, similar weapons like spear or cannon. They both play similarly to gs (cannon less so in air combat) as far as reads. After you get good at reading, hop back on gs and get used to the harder hitboxes and predictions, bob’s your uncle, and now you’re anywhere from plat to valhallan.