How to relay Wi-Fi from the street to the premises using a router and an antenna?

Question

network hardware

There is a room with an iron roof and iron walls.
On the street, at a distance of about 20 meters, Wi-Fi is heard from the window.
There is a reception outside the premises, but alas, inside.
There is also a ZyXEL Keenetic II router. Is it possible to connect an antenna to it to catch Wi-Fi from the street and at the same time distribute it indoors? If so, what kind of antenna can be used for this? Preferably not very expensive, but a finished product, without home-made.
PS I have doubts about the relay function: does it use the same antennas for reception as for transmission? Strongly do not kick for, perhaps, stupid questions - I understand radio communications poorly.