yea i asked myself this question quite a lot of times

i read about it, and they say the universe is probably in expansion, im not gonna tell you the reason coz its pretty long and complicated, and so yes there would be actually an end coz universe is like in cycle, it gets bigger, and then smaller.

"our" universe only exists since --- billions of years, and there was other universe before it

i think that beyond the universe is a fourth dimension, but our brain cant figure it out

anyway im lazy and dont want to type anymore

hope it helps