@woozle 

I don't know which advice helped me but it worked. Thanks.

Now a question: if I connect my pc just behind the router, I get from 60 to 80 Mbps download speed (the maximum is 100). If I use the wired connectivity through the powerline, I get about 20 Mbps. The router room and the extender room are a bit distant. However, can I get any improvement by purchasing better Ethernet cables? Or should I buy a completely brand new (and more expensive) powerline?

Vincy98 wrote

  @woozle 

I don't know which advice helped me but it worked. Thanks.

Now a question: if I connect my pc just behind the router, I get from 60 to 80 Mbps download speed (the maximum is 100). If I use the wired connectivity through the powerline, I get about 20 Mbps. The router room and the extender room are a bit distant. However, can I get any improvement by purchasing better Ethernet cables? Or should I buy a completely brand new (and more expensive) powerline?

  @Vincy98 

Unless your Ethernet cables are more than 20 years old they should be good enough to support the 100 Mbps Ethernet speed of your AV600 devices.

The issue with Powerline technology is that the resulting performance (i.e. speed) cannot be predicted in advance. If you are lucky, then an "AV2000" KIT might triple your download speed, but if you are not so lucky, then even an "AV2000" KIT might still only achieve 20 Mbps.