@Idan99 

Hi, since all the Deco units under the same Mesh would be under the same operation mode, did you want to set up main Deco under wireless router mode and 2^nd and 3^rd Deco under access point mode?

Or set up all three under access point mode and connect both main and 2^nd via Ethernet cable to the ISP modem/router?

@TP-Link 

OK.

So I have 2 floors 

The router is in 1st floor.

I want to connect the main deco by cable to the router  up to the 2nd floor. 

2nd deco to connect by cable to router also to the first floor (it's far from router)

And 3rd deco to the 2nd deco by wireless.it will be in the garden.

What is the best way to do that? :)

@Idan99 

The process.

1. Keep your ISP router in "router" mode, not in "modem" mode. "Router" mode is default mode, so if you haven't messed with your router configuration settings after you added Deco, you are good. If you did, you'll need to undo your changes.

2. Connect the Main Deco to router by cable. Do not connect any other Deco to router by cable yet. Confirm you have green LED light on top of your Main Deco, that means it is connected to router and to Internet. 

Check LED on both Satellite Deco, it should be green, too. If it is not, bring Satellite Deco to the room where Main Deco is, to have them wirelessly connect and see each other.

3. Change Deco Operating Mode to Access Point, see Deco app screenshot below. This change applies to all Deco units in your mesh. Give 3-5 minutes for change to propagate to all Decos.

4. Now you can connect second Deco by cable to router, and it should work.