Is Atl a professional fencer? Cause I seem to remember he is a savage.

That said, you'll have difficulties fencing against a great sword. There's no parrying in that and 1 hit will cut your guts out -- the myth that swords and armor are heavy are also lies. Moving in armor at running speeds is perfectly possible, as is getting up when falling. Same goes for swords, they're extremely light for the way they look. There's no fencing against a greatsword.