Pond help!

Pond help!

Hello, this is my first post, hello everyone! I've just moved, and I have this extremely neglected pond in my back garden. I'd like to strip it all back, clear the water and make it habitable for frogs and maybe even a little fishy. I'm just wondering is anyone has any experience with ponds, and what you would recommend for getting it back on its feet? and also, can anyone identify the huge green plant next to the pond? its over 6 feet tall, and has taken over most of the garden :/ it had huge brown stalks (which had obviously flowered that summer) growing out of it which i cut back, if that helps.
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