Household contents insurance: How do I best prove my valuables?

I have quite expensive electronic devices (PC, laptop, home theater, TV, AV system, various cameras, etc.) and I'm sure that one day my senile neighbor will forget his beans on the stove and burn the whole building down. Since he certainly does not have the means to pay for the damage, I will probably stay at my expense without home insurance.

I have copies of the purchase receipts for all valuables both on a hard drive in my safe deposit box and in the cloud. I also have photos of my entire apartment (max. 6 months old). I can't do more than that, can I?

And how do I actually prove cash? I have a considerable amount of cash at home and I don't know how to prove it in the event of damage. So far I have photographed every note including the serial number individually.

Cash is not included in the insurance anyway - anyone can say that. Only very small amounts are covered (up to 2000-2500 euro, depending on the insurance). No photo helps either, it is not covered.

"I can't do more than that, can I?" No more would be an exaggeration

Without home insurance

You don't have to understand that.

no small amount of cash at home

Not that either.

I can't do more than that, can I?

Yes, of course.

That would only be necessary if these "valuables" were lost in a burglary. For all other damage, the items are still there.

You can only really prove with the purchase invoices in your name that you have ever owned these items