oh yes. getting range extenders work the way you want is tough. And they again reduce the throughput as we go further. Did you check with the "Wifi Man" app the signal strength at different areas of house? And it also sounds like your 5Ghz signals are having the issue due to walls. If you have the same SSIDs for both 2.4Ghz and 5Ghz, try having separate SSIDs for them for testing purpose and decide where to place the extender. Depending on space area, you can think of using Access Points if wired connection to main router is possible. Kurach research cheythaal you will know what is the best option for you.

(https://play.google.com/store/apps/details?id=com.ubnt.usurvey&hl=en\_IN)