I gave up. Created an internal network with 2 computers and 1 Deco. no change in speed... Last attempt I did, i took mr Archer C6 instead of Deco and get again 950 mbit/s... sorry guys, sending you...

@ImtiazAli no change. tried again config with single main deco + then with all 3. 99,6 Mbit/s is maximum I get. Now Im running w/o switch, but still the same. I also switched Decos and re-configured...

I bought Deco M4 recently (FW 1.5.6 Build 20221229 Rel. 72252) to extend the network coverage, but cant get more than 100 mbit from it. Configuration Main TP link modem -> TP-link 1Gb switch -> Deco...