The Universe is not expanding - it can not.

The Observable Universe is expanding - which is the remnants of Big Bang

It's not expanding into space. The space (and time) within our universe is expanding. Current theories suggest that the singularity at the origin of our universe was / is the result of a collision between two other universes or is contained within a black hole that resides in another universe.

As I understand no. The universe is like an expanding balloon. If you draw dots on it before blowing it up, the dots become further apart.

Or to?

No, there is no middle point to infinity, think about it. if there is no boundary, how can it have a centre?

What is it expanding into?

Who knows my friend....we have scientists word for this opinion of the universe is getting bigger by something ridiculous like....100 million miles a day....how they truly can work this out I have no idea....they don’t even know where the universe begins and ends.....all they have is theories.....I get for example how they know the size...speed and area of the moon....I watched a program on them working out the math....but these theories of black holes...which professor Steven Hawkins again can only speculate and theorise on....and suns and galaxies beyond our galaxy....which according to a physics group I follow on fb....speculate and theorise that to move outside our Milky Way....is something to the extreme of 100000 light years....but ....science is beautiful....I was once told...if u want a job....become a scientist.....there will always be questions asked and questions answered....

Scientists call it dark matter, but aren't really sure exactly what the cause is yet.

We've known that the universe is expanding for decades... No void.

Nope..just like there is No center in an expanding balloon..the universe is expanding in all directions simultaneously..