My first language is spanish but i'm gonna go ahead and write in english so other people can read this as well
I think you need to be careful a little more with how you pronounce the words in spanish, talking is completely different to singing, and when you sing in spanish, you have to be really careful with how you pronounce every word so it can be understood well.
There are certain words that one can't really understand, even as a spanish speaker, so be careful about that.
As for the voices, I think the second voice might be too much over the main one.
Still regarding the second voice, be careful with the timing of it so it doesn't sound like it's falling behind as well.
I will go ahead and say that I agree with what the other guys have said, the voice needs some reverb, you don't have to add a lot to it, just a little to give it a really gentle, yet not saturated, echo. I second Thunder Dash on this as well, if you want the song to have a little more of a "sad" feel to it, it would be nice to slow it down a litte bit more.
Also this is a really small detail but i'm sure the song could sound better if you fixed it. There's this little slide on one of the voices that sounds too deep when you say "Oh" on the "Oh hermana, que ha pasado?" part. it sounds a little weird and that was the first thing I noticed when i heard the song that i thought could've sounded better.
Please take no offense of this critique, then again, we're all here just trying to help and promote improvement c: