so i paint my bike plastic panels black pearl and finish with universal clear from **********.
12 hours later i wet sanded with 800 and 1500 grid paper.
buffed with rubbing compound on yellow pad and finishing compound on black pad from turtle-wax.
I cant match gloss level and black level of finish compare to original panels or panels just after cc.
what are right steps , hat do i do wrong.

You should consider switching to professional products for buffing.,

Or a better clear. Not a rebaged inferior clear

Before this turns into a flame thread...I really don't think ********** is 'rebadged' clear. If you have facts to back that up, state them, otherwise I don't think you should disparage a brand that way.

Meguiars 105 on a Lake Country yellow or possibly orange (a bit less aggressive) will put the 1500 grit scratches out and leave a pretty decent finish. Work the 105 until your sanding scratches are gone. It'll take fairly high speed and a bit of pressure so if possible put the pieces on the bike. If you're having trouble getting the scratches out you might consider going over everything with even finer paper or sanding discs.

After 105 you can follow up with 205 (on darker colors you'll be glad you did) and it'll look awesome. Griots Garage sells a nice little 3" orbital buffer that is pretty handy for bike parts.