The whole module is inspired by the pull-Request by "therool" which did the pull-request here
The only thing i did is to put his code in a working magento2 module to give currently running shops a working paypal payment method.
Install this Module as every other module in Magento2:
- composer require {Module_Name}
- ./bin/magento module:enable {Module_Name}
- ./bin/magento setup:upgrade