Guys, thank you for all the answers!!
eschwartz: I tried the firefox android app, but although it has some extensions/addons for android, there isn't the 'send to kindle' extension. Even using the desktop mode as you said, I can't do it.
Edward_R and mystika1, thanks for the suggestions of the app. In fact, I had saw these apps before, but since "Push to Kindle" wasn't free and "Send to Kindle" had a description saying you needed an account on a third-part website (which wasn't free) I always looking for some free way to this before trying an paid alternative. But I went to play store again and the "Send to Kindle" app altered its description, removing that part that said it needed the third-part paid account. I downloaded it and it has been working. Thanks for the help!!
PS: looking at the play store, i found a new apple (released this month) that says to do the same thing, but I didn't tested yet. Anyway, if someone wants to do it, here is the link:
2 Kindle