As someone who wasn’t alive at the time, I don’t understand why people couldn’t have just ridden a car or bike out of the city and driven back to the other side, or why they couldn’t have just climbed the wall.
Hi there -- not to discourage further answers on this topic, but this has been asked here before, and the nature of the wall (not just something you put up to keep people out of your garden, but a fortified border that encircled West Berlin) has been discussed here before:
and in this illustrated answer from u/kieslowskifan: