"the problem is that when i push the pedal down i still hear air inside when pushing the pedal down"
Is this a constant hissing sound if so the new booster is faulty.
It sound like you still have air in the lines.
Start at the M/C crack the front line have someone press(steady pressure) the pedal to the floor and hold it. Tighten the line repeat this until you have a constant flow of fluid. Once you have a constant flow tighten the line before the pedal reaches the floor.This will reduce any chance air getting sucked back into the system. Than repeat for the back line . Next move to the r/r wheel bleed the same way only using the bleeder screws, next do the L/R than R/F ,than finally the L/F. At this point you should have a good pedal. Than I go back to the wheels in the same order have your helper pump the pedal 3 times and hold, crack the bleeder, once you see a steady flow close the bleeder, again before the pedal goes all the way to the floor. Constantly check the fluid level don't run the M/C dry. Good Luck
