I'm afraid of losing the warranty for not doing the 1st review, in the US you lose the warranty if not the review?
There are lots of owners that do all the services on their own bikes themselves, including the First service. Here in North America doing your own services as required with the proper lubes/filters does not void any warranty. That being said it is important to keep all your receipts for purchased lubes/filters etc and document the services and mileage at the time the service was completed. Normally good documentation will preserve your warranty....but it might provide a good excuse for your dealer to give you grief. What would happen in Brazil only you might know better.
Dutchy