Well first off, you must have gone to the wrong site! There's no Italian to be found on my site, www.adgshop.com
There are guides for amounts to use as well as detailed explaination of the substrate system, application ans usage.
Here I can tell you that for your sixe tank you will need:
1- 18 liter bag Power Sand SPECIAL "L"
9- 9 liter bags of Aqua Soil NORMAL Type.
1- TOURMALINE BC
Powder type Aqua Soil is used as a very topmost layer for primarily aesthetic purposes. though it is quite useful for keeping the fine runners of plants like hairgrass closer to the surface (keeps them from tunneling into the substrate as much). Depending on the layout style, Powder type Aqua Soil may be used just in the forgeround section. If you choose to use it, either sub one of the 9 liter bags of Normal type or simply get an additional bag of Powder type, 9 liters size. It also comes in a 3 liter size, which may be good also for a more limited area of use/application within the layout.
The order of placement is:
Tourmaline BC on the bottom glass
Power Sand SPECIAL next
then Aqua Soil to the desired depth/slope on top.
Let me know if there's anything else, and try checking back on the website. You can also link to ADA products availabilty through our main site at www.aquariumdesigngroup.com