Question: 1 When I was your age, there were 3 billion people on earth. Now, 35 years later, there are 6.2 billion. Everything is relatively fine--or at least relatively unchanged. Possibly the same will be true when there are 12.4 billion. On the other hand, maybe there will be a huge bird flu plague and 6 billion people will die. Nobody knows. It's impossible to answer this question.
Question 2. Mother nature is VERY good at keeping things in balance. It's more likely that "she" will kill some people before allowing a very huge imbalance. Again, nobody knows. This is a mystery and nobody can answer this.
Question 3. Again we don't know. Perhaps we are causing global warming. On the other hand for 300 million years the earth was a greenhouse. That's why there were dinosaurs and so many plants that became oil. Maybe we are just headed for another 300 million years of "ordinary" greenhouse conditions. The cold state of our planet now is NOT the normal state if you look at things on a geological scale--on an Earth scale, not a human scale. We are just coming out of an ice age that lasted ten thousand years which barely counts. Anyway, nobody knows the answer to this question. We could be going back into another ice age, or into a warm period. Odds are it will be warm since for most of the planet's existance it has been so. Humans have hardly been around for a speck of time when you look at the grand scheme of things.
4. What is being done to fix this problem, to heal the world?
There is something called the Kyoto Accord where most of the nations of the world (except for the USA) have agreed to cut back the rate at which they burn fossil fuels and create CO2. http://unfccc.int/essential_background/items/2877.php You can also visit websites of environmental activists such as David Suzuki. http://www.davidsuzuki.org/ They are trying to do a lot. You can join them.
5. Will the human race ever reach extinction? Almost certainly yes. Virtually all species eventually do go extinct, except certain kinds of cockroaches and hardy crabs. It might take a long time for us to go extinct, so I would not worry about it.
6. If we contiune our actions of killing the planet, will the world come to an end?
No. I can say this with complete certainty. Much worse things than humans have affected the Earth (e.g. hits by giant asteroids) but it has survived. It will easily survive humans.
7. Can we find a better and more efficient way to use the sun's energy to produce electricity rather than let the plants convert them into heat?
Yes. Certainly. However, we have to WANT to do it. Unfortunately for the time being, oil is so cheap and easy to get that nobody really wants to try. Possibly people will try when all the oil is gone.
8. Is the earth's food supply in danger? Nobody knows. In general it seems that there is more and better food now than ever before. However, much of this situation is supported through the use of oil. When the oil runs out things might change. But that might take a while.
9. Will there ever be a cure or treatment for every illness and disease? Can many people who deserve to live be saved? No. There will always be disease. Disease is important. Kind of like night and day. You cannot have day without night. And you cannot have health without disease. A lot of diseases are good because they make you stronger.
As science and medicine get better, more and more people are being saved, and this trend is likely to continue.
10. Since the rate of birth is higher than the rate of death, is it a good thing or a bad thing to control the population by giving the death penalty to the people who deserve to die? will this action help steady and balance the over population crisis? Can the human race ever reach the stage of equilibrium?
It is always a bad thing to kill people. Even if they "deserve to die". Nobody deserves to die. Even if accidentally one wrong person is put to death by the death penalty this is a VERY bad thing. The number of people that could be killed this way would be so small it would not affect the global rate of population growth. A better thing to do is to educate people and to give them a better standard of living. The only countries in the world where there is a high population growth rate are the poorest countries. In Canada and Europe, population growth rates are negative. The human race can certainly reach a state of equilibrium. Some current studies show that global growth rates are already slowing.
The best thing you can do to change the world is change the way you yourself behave. Do not buy a car. Do not watch TV. Do not use more than one or two pieces of toilet paper every time. Do not buy Macdonalds hamburgers. Etc. There are TONS of things you yourself can do to help save the world.