Hi Wonderfull - I am not sure which bridge you mean but here is some help:
SPOILER:
Run and get the bonus coins, quickly push the box up onto the conveyor - follow it quickly and push it onto the second conveyor and into the water. before you follow it - step on the blue timer switch, go down the conveyor and step on/off the round blue button to activate the gate and keep it open.
Now use the two useable boxes and push them into the water and push the boulder round to the left to smash the third box on the left edge so it sits on the red button. The gen will start - use the middle box to make a bridge by the blue TP so that you can go through the TP and use the next box by the gen - always remember to step on/off blue round/timer button to keep the gate open!
Use the next box to build a bridge to the area where the two barrels are. There is a boulder hidden in the wall - use that to smash the remaining box by the first boulder to start the generator again. Go through blue TP again and repeat using this system to fill water by kaboom and let him out to explode barrels!
Hope that helps - ask me again if you are still confoozled
