Help, why is colour fill working in lines?

I’m new to this and whenever i try to fill a space it does it in lines moving in from the border. I want to fill the whole thing in a single colour. Sure there is an easy explanation would be grateful to get an answer. Cheers.

What version of blender is this, and is there a reason to use grease pencil instead of a mesh?

Blender 2.8. Was using grease pencil because watched online tutorials saying it was the best way for 2D animation.