Because you haven't reviewed the videos at the start of this thread. We get this from observation. Mountains of biological and paleontological evidence bears out the facts of evolution. There can be no question of its veracity, only of one's comfort with the facts. Please review Potholer54's Made Easy videos on Evolution and Human Evolution, #'s 7 & 8. Please also simply type "evolution" into Wikipedia for direct explanations, plenty of sited sources and further links.
Unfortunately, you have exposed that your primary sources are sadly misinformed or at least uncomfortable with believing in reality, and I find it particularly sad that these people are educators (not biologists though thankfully). To debunk many myths associated with evolution please review the links on this page:
An Index to Creationist Claims
As for the Time magazine article (which is completely unrelated to evolutionary theory BTW, but is often challenged in the same breath by creationists because both refute the biblical creation myth), it is not directly creationist propaganda, but when edited by people who think as your teachers have, it's easy to understand how a scientist's possibly valid work (I haven't read the book so I can't comment on it) can be ridiculously misrepresented. The Time article is moronic. It may be that the title is there to attract readers, but it is misleading as I think is the title
The Selfish Gene. It implies that there is a gene for selfishness and that naturally we are selfish creatures, which is not the point of that book as I understand it. The title of the book in the Time article is even more misleading though.
What Came Before the Big Bang is an impossible question. It ask about something before space/time. There is no
before time and there is no
thing outside of space. Indeed as cosmologists look further and further back in time (which is equal to further away from us) there comes point where space/time breaks down and there is a wall of evenly distributed
background radiation. It is theorised that at this point which were the earliest few seconds (perhaps microseconds) of the universe,
the fundamental forces at work in our universe were operating together as one force. The nature of reality would be completely different than the one we now know. Space/time was a radically different place. This is almost a 'before' for time, but probably not quite. Before that? Not a valid option. Simply put, there is no chance for a 'before' without time. There is no chance for anything to exist without a place for it to exist either. If that idea addles you mind as much as it should (it does mine) then you are better able to appreciate the awesome genius of people who dabble in such cosmological mysteries.