your problem is different.
your tp-link router is not "directly connected" to internet, i mean it doesn't get a true internet (external) address.
So, you are connected to another router.
Ask who is managing that router to open/forward the port for you.
Possibly this router is actually your ISP, and they may not offer this service at all.
In italy there is a company like this, and they offer internet ip as an extra service to pay.
Good luck