Catalyst Converter On T Sport

[Wilz T Sport+R6]

hi ya there guys. would like to ask for some advice on my catalyst,

its apparent that my CAT is on its way out, its making some weird rattling noises, corresponding to throttle. ive had a look under the car, and the cat seems to be part of the centre pipe as well, now can any1 advice me how to replace one? or may be de-cat the tsport? i did notice the oxygen sensor right on the cat, i would like to know how to tackle that too.

many thanks