New old caravan bought. Electrics 1×1

Hello dear ones! After reading for days I have to open a thread. I have read so many articles about WoWa Elektrik that I now know which possibilities there are, or systems, but still do not recognize how the existing (or not existing?) system works. We recently bought a Bürstner City BJ. 82. Now we have been busy renovating for some time now. The topic of “electronics” is about. I suspect that there will be a lot of problems. please help me and explain what you see in the pictures here and how the whole thing works together and above all – how and where does a battery come between? I am very confused. And how do I find out if the 13pin plug is already set up in such a way that the alternator of the towing vehicle could charge the WoWa battery if necessary (provided that the booster)? To the project: We would like to equip the caravan with a system, which For max. 4 days Autark can be used. Consumers would be 12V consumers like LEDs and chargers, but also 220V like for example a sandwichmaker or similar. Here are the pictures. Below the bench in the rear are some cables. These lead under the sink to a voltage converter, from there to the wardrobe, in which a fuse is installed (or 2?) Up to the two photographed cans. Does the battery come between there? From there it goes on to the Outside connection for electricity. What exactly did I photograph there? Thank you in advance Best regards, Alexander