Some little questions, please answer

so we did an experiment with a bottle rocket (2 L bottle, empty) we went outside and we registered the time the rocket flew (5,43 sec) that means that it took about 2,7 sec. to go at the highest point and about 2,7 sec. to go down.

Based on this time, try to find how high your rocket went (which was about 60 metres) but i still do not understand how to find the energy that it has at the start, how can i figure this out? how long a 60W light bulb would last if it was powered by the same amount of energy?

then: how do these sounds travel to your ears (any sound)? what do these noises tell you about what happens to the air and water inside the bottle? what does happen to the air and water in the bottle as the rocket goes up, goes down and hits the ground?

THANKS, I'LL GIVE 10 POINTS AND 5 STARS WITH CONGRATULATIONS!

I'm not sure you can say that time it takes to get to the highest point is the same as the time it takes to get down again. That's only valid if the acceleration is the same during the ascend as it was during the descend.
Since you already seem to know the height, you can get the energy from the formula E = m g h, where m is the mass, g is the strength of the gravitational field and h is the height.
A Watt is the same as Joule / s, i.e. E / T, where T is the time the lamp is on. So, 60 = E / T ==> T = E / 60.

I'm not sure what you mean by 'how do these sounds travel'. Sound is nothing more then pressure waves in the air. I don't know what the noises tell you. Presumably you can hear when the rocket is out of fuel when the sound changes?
Anyway, during ascend, the air inside the bottle is expanding due to the high pressure and as such it thrusts the water out of the bottle. Since according to Newton, action is minus reaction, the bottle itself is pushed upwards as the water is pushed downwards. When it goes down, nothing really happens to the water of air, since the water is all gone from the bottle now and the air has the same pressure as the surroundings.