How to make a key act as acute and apostrophe? dead keys problem
Ok, this is not the answer, this is some kind of "workaround" that I don't like. It works but makes me memorize another super key combo.

# In the keycharmap I puted this:

# this is the default for this key
key GRAVE {
    label:                              '`'
    base:                               '`'
    shift:                              '~'
    alt:                                '\u0300'
    alt+shift:                          '\u0303'
}

key APOSTROPHE {
    label:                              '\''
    base:                               '\''
    shift:                              '"'
    alt:                                '\u0301'
    alt+shift:                          '\u0308'
}


And with that settings I get this results:

Alt+APOSTROPHE A = á
Alt+APOSTROPHE O = ó
Alt+APOSTROPHE Shift+A = Á
Alt+APOSTROPHE Alt+APOSTROPHE = ´ (lonely acute)
APOSTROPHE = '
Alt+Shift+APOSTROPHE A = ä
Alt+Shift+APOSTROPHE Shift+A = Ä
Alt+Shift+APOSTROPHE Alt+Shift+APOSTROPHE = ¨ (umlaut)
Shift+APOSTROPHE = "


Using Alt+Shift feels unnatural and I'd like to get the same behavior that I've got on my PC, but for now this works.