Power Shower Combi Boiler I Want To Install Another Power Shower But I Have A Combi Boiler?

I want to install another power shower but I have a combi boiler? - power shower combi boiler

I would like to install one in a bathroom, 1 shower shower, but I've already been to turn the shower faucet from hot water. What can I do to the loss of heat and pressure showers ????????????????? prevent