I have a TP-Link router with DSL service provided by a local company which serves it over the landline phone. My landline cord is plugged into an ethernet router which is then plugged into TP-Link wireless router. I can access internet with this wireless router all over my home with all computers.

Landline Cord [into] Ethernet Router [into] TP-Link Wireless Router [air] Computers

I would add that landline cord is also into a phone device which I use to make calls and that's not cordless.

Now I am accessing internet via WiFi on my laptop and want to ask if is this possible to make landline calls via this same computer I am surfing internet through? What I am asking it to a dial-up via TP-Link router that goes through landline. You see the landline cord is the actual data gateway and is also used to make calls. So it can simultaneously send Data and Voice over the same wire.