How to waterproof a nubuck boot without it losing its breathability?

Hopefully this will help:

http://www.lowa.de/en/products/service-care/care-tips.html

Good luck!

A good trick is to use toilet wax ring. Wipe the boots clean and set them and the wax in a warm place, near a heating vent, in the sunshine, or near a woodburning stove. Don't get them hot, just nice and warm to the touch. Then, using your fingers or a small cloth, rub the wax into the leather. If you don't want to waterproof your fingers, wear gloves. Avoid getting wax on the plastic/rubber parts of the boot. When the boots are nicely coated with wax, set them back in the warm spot for an hour or more - once again don't allow them to get hot. Then using a soft cloth, buff the excess wax away.

Hello Jamal :) Being up in The States, I am not familiar with what is specific to Brazil (even though I do have a long time friend who lives in Rio). When I searched for products specific to Brazil these 3 popped up, so I am posting the links here. Maybe someone else may know exactly what is available in Brazil for your needs. Good Luck :) Thanks for using Hometalk :)

https://www.amazon.co.uk/Brasher-Waterproof-Protector-Spray-Footwear/dp/B005CGMRT4

https://www.amazon.co.uk/Nikwax-Nubuck-Proof-Waterproofing-Footwear/dp/B00RD7RV0A

https://www.walmart.com/ip/Revivex-Nubuck-and-Suede-Boot-Care-Kit/21970268