Hi @marcoooo first you need to know the infolabels that you can use. to know that you can see the code of the Debug view, that you can find HERE
you can find labels like ListItem.Art(cartridge), ListItem.Art(map) and so on. probably you need to create a custom window too, don't know if the skin that you are using has info page on programs.
Kodi wiki is a good place to start and see a lot of information, edit some stuff on your skin and see what it does. remove some blocks to see why they are needed. I learned that way. I'm not a skinner either.
If you need help with coding you can ask either in the Skinning forum or you can send me PMs. But most of the work need to be done by you. On the first few days you start slow, but with time you will learn a lot and will be easier.