According to the new testament, how and when was the world made?

Basically, most of the Christians who argue with me about gay rights and creationism will also tell me that the new testament is the one we go by because it’s the one that was written after Jesus in the true spirit of Christianity.

Based on this, if I was a believer, I wouldn’t be able to swallow the creation myth because the old testament was overwritten by the new testament in a lot of places.

What about when it comes to creation?

Since Jesus was a preacher of the old testament, should we accept the old testament as gospel when it comes to the creation story?