How to control gear walla bike during traffic ,turns n i know how to speed up but how n wen to slowdown.plzHLP

JUST STARTIN TO LEARN GEAR WALLA BIKE..i cn finally start it..wen to go frm 1st to 2nd..but wen deres traffic or turns i find it diff to slow down n wen i do d bike just stops..plz help me..i m studyin in a village area n bikes r a necesssity there