Non-mandatriscript-verify-flag (invalid schnorr signature)

I’m trying to put this in PSBT:

1. Alice pays to buy a BRC-20 quantity from Bob
2. Bob requests to occupy a BRC-20 transfer using his burner account
3. Burner carries the transfer of the BRC-20 and transfers to Bob
4. Bob transfers BRC-20 to Alice

Bob created and signed a Burner account with PSBT. Then send it to Alice, pay it and sign it. Alice Topup on Price covers network fees for all of the following transactions:

The problem I’m currently facing is how to get the required input UTXO PARAMS from the previous output? Could this have been using Bitcoinjs-Lib or the recommended library?