Hi, the sun is the only star in our solar system. This means there are tons of other stars out there in the universe and some are way bigger than our sun.
This image below shows some of the other well-known stars and their relative sizes. the sun is tiny, somewhere there in the middle of the image. Maybe these stars might have their own solar systems too with planets. we've termed every other planet that isn't in our solar system as 'outer planets'

[Image: GiovanniMartin16 CC BY-SA 4.0.]

Since the sun is all we've got, there's no replacement for it if it dies. And dying means a lot of chaos for earth and the planets in the solar system. without the sun's energy-giving rays of light, earth would become dark without daylight and the atmosphere would be as cold as your deep freezer.

If it explodes into a supernova, however, the light would last for a couple of years and we would all be rotisseries on a spit. We'd roast from the immense radiation and heat that would bust our magnetosphere and wear out the ozone to reach us directly. It's game over.

I suggest you do more research on the question though. I found some reasonable articles on quora.

Thank you for reading.