How to change the fire sprinkler?

You mean the fire sprinkler? This is generally operated by professionals, so it is not recommended that you replace it yourself.

The specific steps are as follows: close the main spray valve of this floor, drain water, replace the nozzle, and open the main valve for water pressure test. If there is water leakage, repeat the above procedures, and the water pressure test will be qualified if there is no water leakage for more than 30 minutes.

Because it involves public parts (main valve, etc. ), and it's not easy for you to pay for a nozzle, and you don't know the model and specifications. It's better to find a property company to repair it.