Question about infinity

Hello Rabbi,
I recently began to engage with the philosophical topic of infinity and came to the conclusion that, unlike other abstract concepts that can be seen as having real applications in the physical world, such as time, colors, and numbers, infinity is impossible.
The first reason that made me think this is that we have never seen actual infinity in physical reality, but only theoretically (for example, you claim that there are infinite points on a parabola, but you don't really reach all of them…)
A second reason is that I saw all kinds of paradoxes, such as x = x*x x equals infinity.
A third reason is from Zeno's paradox, which states that it is theoretically impossible to traverse any space because you have to traverse an infinite number of length units (whether constant or not, it doesn't really matter now)… My answer to the paradox was that the questioner implicitly assumes the actual existence of infinity in space even though there is no reason to assume this, and from that I also came to the conclusion that there is no actual infinity in physical reality, otherwise we could not reach any point.
I would like to ask whether you think infinity is applicable in the physical world we know or not?
PS My friend told me that the Big Bang theory is not really well-founded and that it is simply a default choice even though there is nothing better. Is it really not well-founded?