With extenders, a certain reduction in the data rate is normal, but this difference seems really high. The most important thing would be to position the extender optimally. You can also find instructions and tips on this at https://www.tp-link.com/de.... You should be able to judge whether the router signal is sufficient by the LED display. For further assistance, it is best to contact our customer support https://helpcenter.digitec.ch/hc... - then we could look for an individual solution.