AC68U Connect to existing wifi network

[alexsu10]

Need a little help trying to set up my new AC68U router.
My internet connection was provided to me by an existing wireless network which is not mine so I do not have access to its settings and/or network cable.
I bought this AC68U in the hopes that I could connect to the existing wireless network for internet connectivity while all my other devices connect to this AC68U via wireless. Ideally, any DLNA media sharing or SMB media sharing is contained within my own wifi network, not visible to other clients connected to the existing wifi network; only to clients connected to the AC68U wifi network.

Could this be done on this AC68U and if yes, how? Thanks.

 

[alexsu10]

Kindda got it to work somewhat.
I used another mini TP-LINK router and set it as wireless adapter mode.
So this TP-LINK connects to the main wifi network for internet via wifi.
Then the LAN port of this TP-LINK is connected to the WAN port of the AC68U; the AC68U is set to router mode.
Internet connectivity when ios devices are connected to the AC68U wifi is fine, getting download speeds of around 20Mbps.
But, when my Windows 7 laptop connects to the AC68U wifi network, the download speed is less than 1Mbps. Why is that?
Other features like Windows share from laptop to ios works perfectly.