@AntonSar 

hello

1. Set Up the Archer AX80 (Main Router)

• Ensure your Archer AX80 is connected to the internet and functioning normally.
• Configure your Wi-Fi network name (SSID) and password on the Archer.

2. Connect the Deco M4 via Cable

• Connect an Ethernet cable from any LAN port on the Archer AX80 to a WAN/LAN port on the main Deco M4 unit.

3. Switch Deco to Access Point Mode

• Open the TP-Link Deco app on your phone.
• Go to the More tab in the bottom right corner.
• Select Advanced.
• Tap on Operation Mode and change it from Router to Access Point.
• The Deco will reboot to apply the changes.

4. Match the Wi-Fi Settings

• Once the Deco reboots, go to the Wi-Fi settings in the Deco app.
• Change the Deco's Wi-Fi name (SSID) and password to be exactly identical to the Wi-Fi name and password of your Archer AX80.

Hello, will it work like Mesh System, without etehernet cabel between AX80 and DecoM4 ?

  @AntonSar 
No, unfortunately, it will not work wirelessly as a Mesh system.
The Archer AX80 and Deco M4 cannot talk to each other over Wi-Fi to form a mesh. If you don't connect them with an Ethernet cable, the Deco M4 will not have any internet source to broadcast.
To make it work completely wirelessly, you have two options:

1  Stick with the cable: Use the Ethernet cable method mentioned before.  

2  Go all-Deco: Buy another Deco node to replace the  Archer AX80. Deco  units can connect to each other completely wirelessly.