Sounds like you are organized & motivated in your practice routine. That's wonderful!

Originally Posted by: nandre1276

I'm taking notes on what I'm doing to remember how I have to practice each chords changes, here are the two notes, the old one with one or two fingers at a time and the new one with all fingers at once.

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Good deal. Eventually you want to combine those chords into larger groups which is the point of the discussion that follows.

[quote=nandre1276]I wanted to ask you, what does it means when you say key of G and key of A?

A key signature is the scale that all (or most) of the notes & chords of a piece of music belong to.

As a beginner you encounter this concept as chords that are commonly grouped together. They are grouped together because they all have notes that belong to one scale, therefore sound good together & are commonly used that way.

Lisa covers them from a beginner perspective in her GF course starting in Chapter 6.

https://www.guitartricks.com/course.php?input=fundamentals1lisa

But for now it's okay for you to just keep building your skills at the chords you are working on. Keep practicing them, add more chords as you are able & eventually you will be ready for the various chords grouped in key signatures!