1 is the exhaust manifold flange 2 looks like the flex coupling or a pre-catalyst, 3 is the catalytic convertor 4 is another flex coupling?? 5 is a mid-silencer (muffler for we in the USA) 6/7 is the mid pipe and there are fittings but I can’t really see what those are - maybe band clamps? 9 is a flange 8 is a silencer (or muffler).
If you touch anything in front of 5, you won’t pass MOT if you are in GB.
You can easily remove 5, the mid silencer and replace it with a straight pipe. That would be cheap but I doubt it would make it sound much better plus you’d likely get an annoying drone inside the car. That is why its there. Replacing both rear silencers with sporty ones would make it sound a bit louder but may also make it sound fart-y as the others suggest. And it would cost quite a bit. Too loud and you may not pass MOT.