Improving the quality of cellular communication. What and how?

Question

mobile connection

Hello.
There is practically no connection in the office ..
I read about GSM repeaters .. I read somewhere that a cheap repeater supports simultaneous work with only 3-5 devices ... But you need somewhere around 15-20.
Do you have anything suitable in mind?

Answer 1

8k is cheap. GSM Signal Booster Repeater 2G 3G Amplifier / 4G Mobile Phone 900 DCS LTE 1800 WCDMA 2100 Tri-Band Cellular
https://s.click.aliexpress.com/e/cgyQdnXy
It has up to 20 phones write.

Answer 2

Buy two femtocells.