Valve launches Steam Trading Cards, a gimmick to get you to play

Valve lance Steam Trading Cards, un gadget pour vous inciter à jouer

I do not like this beta and I want out of this beta test and find my old profile.
how?

You can't, you are doomed to the new profile for eternity and sooner or later everyone else as well because once the beta is over every steam profile will be updated to the new system.