Below you find the links to the manual of the APN settings on your TP-Link device. First create a profile with TP-Link (step 1), then you can define a new APN in your TP-Link account (step 2).
Step 1: https://www.tp-link.com/de/support/faq/957/ or attachment Anleitung_Schritt 1.pdf
Step 2: https://www.tp-link.com/de/support/faq/1296/ or attachment Anleitung_Schritt 2.pdf
Our APN information as follow:
User: (leave field empty)
Password: (leave field empty)
Important: Authentication Type: Select PAP instead of CHAP