I have a chines scooter 125 cc and I need more power,How can I get it to go faster.Hard to find parts for it?

chinese scooters usually have the same parts as aprilias do your homework first before you buy, ie take measurements. change your end-can sports exhaust variator cavilar belt rip out your normal air box and but in a cone filter many companies do different sizes so they are easy to find. the only problem with going for more power is you need bigger brakes.

travel downhill

Only drive downhill.

That was your first mistake - buying a Chinese scooter! (good luck getting parts for it) The second is...well, I'll let you find out for yourself. OK, I'll give you a hint - trani, clutch and drive belt.
Dinli (chinese) quads put restrictors between the exhaust pipe and the cylinder. Check if your scooter has one. Remove it if it does.

restrictor in downpipes or inlet manifold, try gearing it with the drive and rear sprockets, not a great speed improvement thou.

You bought a Chinese scooter? Well, there's your problem, matey.

Parts are notriously hard to find for these things, so whether you need more power, to to replace worn-out components, you're doomed. You'd have more luck finding gold in a muck spreader.

It probably goes as fast as it's able to by design. There's an old saying, if you want a faster bike then buy a faster bike.