Help? how to beat the double fianchetto


support your center pawns and get developed

Your main problem wasn't the double fianchetto, it was that you left a lot of pawns and pieces unprotected, and overextended looking for attacks. The purpose of placing a pawn in the center is to gain some control over important central squares. Your problem is that you didn't adequately protect these pawns, so you lost them and then had no central control. You should work on making sure that your pieces will be defended adequately when you move, and try to consider what moved your opponent might make and how to prevent them from winning material. Take more time to make your moves.
Here is an example of a game where my opponent had a double fianchetto, but my control of the center was good. Neither of us played perfectly, but it's still an example of how to play I guess.
https://www.chess.com/daily/game/172672808