How prevent my user to pay trxn fees through metamask

Question

I have deployed a contract using an account (pool account,let say pool=0x1234).

I am creating a dapps and giving facility to my user to mint/transfer erc721 token. My issue is that I don't want my user to pay any amount from their account to process a trxn through metamask. I want to pay the trxn fees from my pool account. I have an api ready to interact with my pool account. Creating tx object and sign it using my pools account pvt key and submit the trxn using web3 is working fine.

Current flow in dapps:

• when user clicks on 'mint token' button then -> 1.calling contract mint func 2.metamask popups and ask for confirmation. 3. User confirms and trxn submit 4. Trxn fees deducted from users selected metamask account (I don't want it, instead I want to pay trxn fees from my pool account)

Hope my question is clear to all Thanks in advance