How should I setup the network access points in a small business located in a basement with thick concrete walls?

Hi all, I’ve recently been tasked with trying to improve a small business’s Internet. The business office is downstairs in a basement littered with thick brick walls. Currently they have one router (very old, only supports 108 mbps) located in a central room, but does not output a strong signal beyond the area near the room.

First off, this business will be upgrading their data plan from a measly 15mb/s down (yes, it is that low) to a modern 300 mb/s.

To give a layout of the basement, there are four employee offices, in pairs. So, two of the employees directly neighbor each other in one section of the basement, and a little further away, the other two employees neighbor each other.

The way I had thought of doing it would be to place three routers in total in the basement. Put one in each pair of offices, so the pairs would share wireless signal. Then place the third router on the farther side of the basement away from the offices for use in that part of the building.

Now I’m not genius, but I have been tasked with this so I want to give the best opinions and knowledge I can. So id like any input I can get. Should they use just one router, and place WiFi repeaters throughout the basement? Or should they use multiple routers instead?

Thank you all. Any recommendations, layout, devices, etc. are very appreciated!