[X] Grab greatsword, but stay to catch your breath and see your surroundings, there could be more enemies watching.
-[X] Talk to this Astora while giving his/her weapon back, ask what is his/her purpose, if she/he is going the same way you are, you can use him/her as a teammate to make the next fights easier, if not then just sate your curiosity and continue on your way.