We do not know how the Universe came into being and we do not know if, or how, it will end.
By examining how things exist now, and taking detailed measurements and doing complex calculations, physicists are trying to answer these questions.
The most widely accepted theory for the origin of the Universe is the Big Bang theory.
Even assuming this theory is correct, it has, so far, been impossible for scientists to determine whether the speed of expansion of the Universe means it will continue expanding for ever, or reach a point at which its overall density cannot overcome gravitational attraction between all the mass in it, and collapse back on itself, into one big black hole.
This idea is called the big crunch.