I don't know how to write the script :( is there any website I can get the guide or an example to edit or something?

It's not easy because of the security aspect, you are directly working with web3.personal, as in unlocking your account to transfer the funds

not really. You can write a script that exists on a server whose only inbound port is SSH. Have a script that watches transactions, creates a signed transaction, send to infura. Only outbound ports needed are DNS+HTTPS to resolve infura URLS

and you're good to go