The concepts you are thinking about is are some of the most interesting ones in all of science.

How could the universe possibly be eternal? And if it is not eternal, Where did everything come from? What happened before it was created?

One of the answers is that it appears time is something that only has meaning inside a four dimensional, space-time universe, such as the one we live in. In other words, where there is no space time there is no time.

This is mind boggling but there are many things about nature that are extremely weird and counterintuitive but proven true.

For example, did you know that Time runs more slowly under certain conditions?

I don’t mean that something physically is wrong with clocks in certain parts of space. I mean that time actually ticks at a different rate if you travel fast - like close to the speed of light.

This short cartoon explains it nicely:

https://youtu.be/h8GqaAp3cGs

Or something you probably do not know yet that has also been proven is that if you have an absolute vacuum that is 100% empty of all molecules and atoms of any type, at the tiniest, quantum level, tiny particles, both positively and negatively charged, are constantly popping into and out of existence.

You may want to read read Simply Einstein: Relativity Demystified, by Richard Wolfson.