Do you think major pharmaceutical companies withhold certain cures to benefit their own profits?
no, if chemo drugs cost £1000 a pop, they could simply charge £80000 for a cure. they DO and its well known, make marginal changes to drugs to renew the patent to keep prices up and infact charge more for effectively the same drug. IE, some guy makes a drug for diabetes, he gets a 10 year patent, after that 10 years 50 other companies can make that drug and charge less, so in that last year they add a completely useless molecule to the chemical that they prove is slightly statistically better, and renew the patent so they can charge more and also not have competition for the specific drug. Its INCREDIBLY common. whats more the stats don't have to be cooked up, a drug 10 years ago probably gets marginally more effective as they increase its potency anyway and find a way to make it absorb faster or something and thats stats aren't up against the recent improved version but the 10 year old unimproved version. thats capitalism for ya

Remember that for every proper cure and seriously useful drug hundreds or even thousands of completely useless things are made that didn't work, and years or decades of sometimes huge numbers of people go into the research to make the drugs. they do invest billions a year into research to make them and do need to make it back, though they make it back and then some
but eventually other companies come up with similar not quite patent infringing equally good drugs that cut into profits and force competition, so drug companies have no reason to hide cures/drugs , at least not for long
Do you think power companies withhold major advances to maintain their profits?
no, power companies do research sure, but thats probably an industry where more people outside of the power companies themselves do the research into new fuels. maybe they don't research new fuels as much as they could, but thats a far cry from withholding advances. the breakthrough for a "next gen" power source is 99% likely to come from a research team outside of a power company which is completely different to pharmaceutical companies where the biggest cures and drugs will come from within that industry. Guys outside the powercompanys that could come up witha power source stand to make billions upon billions upon billions to find a replacement for oil, they could become the richest person on earth in the space of a few months selling the tech, theres almost no chance that will be withheld.
Do you believe in aliens?
to believe this is the only planet anywhere with life on it is fairly naiive. but then again, one of the planets with life on it has to be the first, thats the way of things. in all likelyhood we aren't the first, or last or anywhere near either. but as someone else said, the likelyhood of aliens visiting here anytime soon, or being close enough to get here, or us having the travel capability anytime soon to get to an inhabited planet are incredibly , incredibly low.
Where do you think we came from?
evolved from some pile of fungus, pus, goop, random asteroid dropping some dna that mixed with something and evolved into us eventually, who knows, who cares. god? no.