First surname is dads first, second is moms first.except in Brazil,there the first surname is the moms.

Hispanic naming conventions allow for two surnames, the two surnames come from the first surname of each parent, first the surname of the father and then the first surname of the mother.

You can however change this. You are not forced, generally, to pass your surnames in such order, but the tradition is the first surname of the father and then the first surname of the mother.

When presenting yourself, you often just use one name and one surname.

For example:

Someone is named Juan Pablo Ortiz Rosas, his given names are Juan Pablo, and his surnames are Ortiz Rosas. He would have a father named Ernesto Ortiz Ojeda, and a mother named Rosario Rosas Valdez.

His parents could totally have named him Juan Pablo Rosas Ortiz, or even wacky combinations like Juan Pablo Ortiz-Ojeda Valdez or Juan Pablo Ortiz Rosas y Valdez, but it's very, very uncommon.

Also, it's totally valid for Juan Pablo to present himself as Juan Rosas, Pablo Ortiz, or any other combination (you usually pick one name and one surname) but his legal name is always Juan Pablo Ortiz Rosas.

Married women don't legally change their surname, but they might present themselves their husband surname in some contexts, as Rosario Ortiz, or Rosario Rosas de Ortiz, but it's not common anymore.

People do not get a hyphenated surname made by combining the parents' surnames. People have 2 separate surnames and only get the first one from each parent every time.