You are right partially.
Heaven and hell are both for eternity, which means that whether we end up in Heaven or Hell, we will stay there for ever.
So yes, our souls are pretty much without end if you look at it that way....but ONLY because that is Allahs will.
That still doesn't mean our soul is immortal...it can be destroyed in seconds if Allah wants it.
So just because Allah wants our souls to be infinite, does not mean that it is "immortal"
The Universe, if it started from a singularity and it is expanding ever since, it means, it must have an end.
That is the logic scientific outcome of that statement.
in other words:
If we assume the whole Universe came from a single point in space after a big bang...this means that the particles are travelling away from that point ever since (expanding)...and that happened roughly 14 billion years ago. The speed those particles are travelling with is light speed MAX.
This means that the max edge of the universe from that point of singularity can be calculated: 300.000 km per second x 14 billion years...
which is a huge number of course but not infinite.