OpenWRT LUCI AP bridge

I have a fast fiber connection (300Mbps) with an modem from the operator and an AP from the operator as well. Problems? The AP is not mine (although good) and network access restriction does not work as it should. Operator is Orange Polska. The AP is Sagemcom device called Funbox (version 2 or 3 - I don't remember). It supports both 2.4GHz and 5GHz bandwidth. It can be used for TV-over-IP access (then 1 or 2 ports are used for some kind of VPN connection - internet knows more about it - I don't as I am not watching TV) and for VoIP telephony (I guess standard SIP). Problem statement: I wish to route my network in my way, not using not-mine AP. What I do have: Several routers. All support OpenWRP, some supports only 2.GHz, some are "dual" with MIMO (faster 5GHz network). My laptop, desktop, cell phone. What I want: Not-mine-AP -- my-AP -- my devices and at the same time I wish to connect my devices (ex. my laptop) directly to the not-mine-AP and see all of them as in one network. What will I do? I will keep updating this post with possible solutions. Solution 1: seamless (buggy) single network.