Which sentence is written correctly? when i was only eight, my grandfather died. while being only eight years old, my grandfather died. when only eight, my grandfather died.

He had fished in the river since ten years and he was a good fisherman. he know where to found the slim sliver chilwa fish, a big beautiful mahseer and the long moustache singhara. he know where the river was deep but where it is shallow; he knew which baits to use - which fish like worms and which liked gram. edit the above