The key looks to be D flat major. I assume you are referring to the G flat accidental in bar 9 of the piece. Like you I’m no expert, but I’m quite sure this means G flat, not G double flat. An accidental temporarily replaces what went before, it doesn’t
supplement it in the way you are suggesting (if it did, the B double flat accidental which you also mention would really be a triple flat because B is in the key signature as well!).
Strictly speaking, the G flat accidental is unnecessary. It is only there because there is a G natural accidental in the preceding bar. Of course, that previous accidental is automatically cancelled by the bar line so the G flat symbol in bar 9 doesn’t have to be there. It is simply inserted as a reminder that we have reverted to G flat and it is what is called a “courtesy accidental”. Often, these courtesy accidentals (which are not strictly necessary but are helpful to the player) are shown in parentheses but they don’t have to be.