Have to agree with the final paragraph of 1BLs’ post.
Having a brand new guitar is a great feeling, but get a few “battle scars” on it and it’s truly your own and adds character.

Before buying another, remove the part and leave it fully immersed in lemon juice (fresh or bottled) for a while. More expensive than vinegar, but better job done in my exp. The surface oxidation will be removed by the weak acid and a little bit of salt actually helps.

Rinse it under good, clean water and, if needed, lightly use an old, soft toothbrush on any blacky gunk.

Might not be “good as new” but should be a definite improvement. Otherwise, just regard it as the “patina” of a guitar ageing.

Sweat causes it, it’s a common problem, the hand is always in contact with the bridge area, most people just treat it as wear and tear, but you can either re-chrome the bridge or buy a new one, no amount of polishing will bring it back.
If you have a new shiny one then always clean it imediatly after playing, and especially after gigs, even between sets, the sweat also kills strings pretty rapidly if you dont wipe them down.