This API extension execute payment to PayPal gateway. It use develodesign/m2-paypal-payment composer module so you have to install it in your Magento instance.

in your local.json file you should register the extension: "registeredExtensions": ["mailchimp-subscribe", "example-magento-api", "paypal-payment"],

And need add the paypal settings to extensions key in local.json:

  "extensions": {
    "mailchimp": {
      ...
    },
    "paypal": {
      "api": "https://api.sandbox.paypal.com",
      "client": "",
      "secret": ""
    }
  }

The API endpoitns are:

/api/ext/paypal-payment/create
/api/ext/paypal-payment/execute