@siamhossain Try this link. There's a newer FW version 1.0.16 here.

@Stary If you're using Smart Connect wireless feature disable that and change the 5GHz wireless channel to 36 - then test again:

@Gangadhar1 If your RE is HW v7 (that's on the botton sticker) update its FW to the latest FW release - TL-WA850RE(EU)_V7_1.0.13 Build 231115 - here. Test again and check if there's an improvement.

@EsDeeEm To avoid the double NAT you could also let your Fritz work in modem router mode and configure AX55 in AP mode (Case 1) - try this and check if there's any improvement.

@LeZs You should probably reconsider the equipment of choice. For a 3-floor house whith 700m2 garden there's an option to use a Deco whole home mesh system like Deco X50-PoE. For the garden you could...

@sunil012 You can click on downside arrow and check for which router models this guide applies to: It apllies to Archers models from AX, C and A series.