Texture image file should not have space. it should be zinc_catwalk_kopie.png instead.
The file is in assets/design_decor/texture/block/zinc_catwalk - kopie.png

Also could you delete src/main/resources/data/design_decor/recipes/item_application/crushing_wheels/special_aluminum_cylinder.json and src/main/resources/data/design_decor/recipes/item_application/millstones/special_aluminum_cylinder.json?
It has wrong item name("aluminum" instead of "aluminium") and it'd have exact same file contents as src/main/resources/data/design_decor/recipes/item_application/aluminum_boiler_special.json if you were to fix it.