You have a bunch of pipes and it is not clear where they run from and to and what exactly they are for. Below I have labeled the pics with some guesses as to how things work. You need to trace every pipe and figure out where they go.
Pipes A, B and C are suction lines pulling water from your skimmer and main drain. They are combined into a manifold and feed water into the pool pump.
The ball valve on A is closed, the ball valve handle on B is broken and we don't know it's setting, and the ball valve on C is open. It is not surprising that the handle is broken as ball valves stick. When you replace the ball valves you should replace them with diverter valves.
Pipe D looks like it is a suction line from your spa and feeds water into the other pump that I am assuming is a spa pump for the jets.
Based on that I am assuming E, F and G are return lines to the pool and spa. But they are hidden behind the pipes and pumps and I can;t see exactly where they go.
There is a crossover pipe from B to D with an open ball valve. That is probably to allow the spa to also draw water from the pool, maybe to run the spa spillover.
Once we get to pics of the pool pump, filter and spa pump I can't see where pipes run back there. I labeled stuff with questions. You need to figure out what runs to where.
There should be a valve on the top of the filter where a few pipes go into. You need to see what that valve is set to.
Trace the pipes and post pics of what you find and let's discuss how your plumbing works.
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