Wow you really suck at philosophy haha.

No buddy, the step between those two premises is probably the least controversial step in this argument.

Contingency and necessity are mutually exclusive and collectively exhaustive. To be contingent you rely on something as as the explanation for you. Necessary means you rely on yourself.

A big box including all contingent facts is itself either contingent or necessary. If it is contingent it must be contingent on something outside of itself, therefore something necessary exists.

If it is itself necessary, then again you have a necessary existence.

It's hilarious seeing someone acting so pompous and simultaneously being so clueless on what they're talking about.