It fixes the Javascript error mentionned under point 7.
It does not fix the other problems though (display issues and functionality of the buttons).
checkout.js:90 Uncaught TypeError: Cannot read properties of undefined (reading 'processing')
at HTMLButtonElement.handler_submit (checkout.js:90:22)
at HTMLButtonElement.dispatch (jquery-1.11.0.min.js:3:8066)
at HTMLButtonElement.r.handle (jquery-1.11.0.min.js:3:4767)
This PR fixes partially https://github.com/pfpayments/prestashop-1.6/issues/5: