Thick walls and wi-fi?

Question

Computer networks

Friends need help.
The situation is this:
a wifi router is installed on the 5th floor - zyxel keenetik giga || - he goes to the Internet to the apartment opposite
on the 4th floor, asus rt-n18 is installed in the bridge mode with ZYXEL, which is above the elevator shaft. - I installed it in the hallway - where the best signal is - but for some reason with large power surges.
he assigned the name to asus in different ways - he gave the same thing as that of the zixel, he gave a different name - the Internet either plows or does not plow.
the feeling is that the laptop is powered by the internet of the zixel, not the asus.
I would love to run a cable to the apartment - but they have expensive repairs and only agree to
wifi
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Answer 1

Install the antenna https://www.youtube.com/embed/-TPq-3XKUNU

Answer 2

What is the problem with running a wire through the stairwell from Zuhel to Asus, going through the wall opposite Asus and connecting it with a wire? There will be no damage to the repair. The hole will be covered by ASUS.
Before drilling the wall, throw the wire just like that and try how it will catch in the square on the 4th floor.
Or did I not understand something?

Answer 3

If you believe the description, the Internet stops working when the signal blocks the elevator itself, because it broadcasts from the elevator shaft. It is not clear who even thought of putting it there, as an option if there is access to the elevator shaft (the router was somehow stuck there), stretch one cable to the floor with a cable and hang a separate router already on the floor.