If Energy Is Constant, Then Why Is The Universe Expanding?

Hi! So, Physics isn't my strong suit, but I realized there were some gaps in my understanding, so I wanted to clarify them here.

The Conservation Law Of Energy states that energy cannot be created or destroyed, so it is constant in our universe.

From my understanding, this law came from several different observations, right? Like how in different experiments or procedures, the net energy stays the same, it only changes form.

So then that brings me to my question:

Does this not contradict The Big Bang Theory? Or the expansion of the Universe?

I'm not really good at grasping Modern Physics, sorry, but I do understand that Classic Physics often work under conditions, like how time is not universally or objectively constant beyond classics.

Hypothetically speaking, is there a way to create or destroy energy then? Like the expansion of universe requires or expends energy, right? So, what is balancing this?

Similarly, does energy stay conserved in the Big Bang?

I hope I worded my questions aptly, I am open to corrections if I've gotten my facts or premises wrong. Thank you!