@Hemaanshuj 

Good day.

Thank you for your patience.

Let me check the following information first:

1. Internet speed from the modem is 1G/S; speed from a wireless router is 600m/s; power-line rate on the utility is 300m/s and the final speed via power-line is less than 20m/s, am I right？
2. The only solution you mentioned is to change the DNS, is it on the wireless router or the computer connected to the power-line adapter?
3. After changing the DNS, how much speed from the power-line then?
4. Since the power-line rate on the TL-PA9020KIT is a little bit slow, please try to relocate the power-line adapter, far away from the large power consumption machine;

(if possible, plug the two adapters in the same room to check the power-line rate.)

Thank you very much.

@Hemaanshuj 

Good day.

Thank you very much for your kind reply.

How long have you had the device and did this issue start since you bought it?

Have you download the powerline utility to see the powerline rate in middle?

tpPLC_Utility_Windows

https://static.tp-link.com/2018/201809/20180904/PowerLineUtility_Win_180816.zip

Have you tried to reset the powerline adapters by holding the pair button for 10s, then pair it again?

By the way, where are you located?

Thank you very much!