Household insurance - How is the settlement of a claim?

I have a question about household contents insurance (HRV) and the assumption of possible damages. Following case:

I conclude an HRV and choose a sum insured according to Wohnflächenberechnung with under insurance waiver.

Now to settle the damage:

Let's assume that I'm being broken into. Then I have to prove afterwards, which devices and valuables were stolen. For this I would have but before a detailed inventory list make best including bills. Otherwise I can't prove that the things were really in the house, right?

Now let us assume that the whole house burns down. Would I also have a list here all (!) Inventory have (including trifles such as more expensive clothes, dishes, etc.), so I can show what was in the detail in the house? That is, will only the sum be refunded, of all that I can prove? Or is the flat-rate value of the sum insured reimbursed here?

What do you recommend to me regarding documentation of the household effects? Do I really have to document every little thing or is it enough to record the big devices (laptop, TV, etc.)?

Mostly through your consultant / broker, because he knows the contract, the office staff, usually also the ladies and gentlemen with the money, and is liable if he has made a mistake on graduation.

My HR pays the necessary repairs and the new purchase, each of course with a bill, up to the agreed sum plus surcharge for total loss.