Wow what a disaster! When I see pics like this I cringe. Just no pride in workmanship at all.
For yours I would start by running the new lines. You can either extend what you have if it makes sense or start back at the pool and redirect to the new location. Once done, cut that mess off below the surface and abandon it.
Here is my plumbing. My plumber was very proud of his work and is considered one of the best in the area.