Hi , I'm glad to see you're interested in our sister planet, Venus. For humans to be able to inhabit Venus, a lot of things would have to change on Venus.

Venus has very active volcanism, no magnetosphere, and an atmosphere full of greenhouse gasses like carbon dioxide, and also a lot of sulfuric acid (acid rain). Those greenhouse gasses and acid make Venus' atmosphere very thick, dense, and it traps heat on the surface of the planet in a cycle that keeps Venus warm. This is called a runaway greenhouse effect because the greenhouse effect increases warming which increases the greenhouse effect in a repeating cycle that is difficult to break unless the greenhouse gasses in the atmosphere are reduced. Removing greenhouse gasses from the atmosphere is difficult to do quickly. The active volcanism, no magnetosphere, and dense atmosphere makes Venus a very challenging environment for life as we know it. If we knew how to change the these things about Venus, we could probably use some of the technology on Earth to help combat human-driven climate change.

Right now, not much. Moving stuff into space right now is so insanely expensive that actually colonizing space is just not something anybody has reason to do. This is why space colonization hasn't happened yet. There are corporations developing technologies with which to mine asteroids and otherwise do things in space that would make money, however, and if these corporations' technologies are successful enough, then colonizing other planets might become worthwhile, but not yet. It probably never will be practical to move people in large numbers from one planet to another, though, so it's unlikely that we could solve Earth's overpopulation problem by shipping half of our population to another planet, though (in fact, Earth would still be overpopulated with only half its current population, and Venus is smaller than Earth, so this would only partially solve the problem even if it were possible).

Venus receives about four times as much sunlight as the Earth does by being closer to the sun. This means that solar power on Venus would be four times more powerful and useful than it is on Earth. Power can be exported from planet to planet by use of a laser, so solar power plants on Venus could potentially be used to solve Earth's energy crisis. The power plants wouldn't even need to be on Venus, though; they could be space stations in Venus' orbit, so cooling off Venus might not be strictly necessary. Still, this seems to me to be the biggest advantage that colonizing Venus would have that Earth does not: a lot more power that we could use.

If Venus was habitable then it could be possible to send humans there to live. However, Venus is a long way away. It could takes years to get there so it would be very difficult to set up humans there.

I think we would need to use so much energy from Earth, to even try to make Venus habitabl, that Earth would not have enough energy to feed us all!

If we cooled down Venus, it would only help us if we did it the right way. The reason Venus is so hot is because it has a lot of greenhouse gases like carbon dioxide which keep the planet really hot (around 450 degrees celsius, 900 fahrenheit).

The best way to cool down Venus would be to get rid of the carbon dioxide. But some other chemicals in the atmosphere, like sulfuric acid, would be bad for us, so we'd need to get rid of those as well. But even right now Venus might not be so bad. About 50 km off of the surface the temperature is about the same as on Earth! If we lived in balloons we might be able to survive there.

I'm not sure if it would be the best for us because the earth is just the right temperature, and it has a lot more water and breathable oxygen than Venus. If we lived on Venus we would have another place to go if something really bad happened on Earth. We would also learn more about other planets because Venus is very different from Earth, and it is more like other planets like Mercury.