Welcome to the Audi Owners Club !
Good to have you onboard
Hello Hamza,
Is the car getting up to normal operating temperature on the gauge or display?
If so, you will need to check if both smaller bore rubber hoses from the heater matrix are of matching heat when the car is up to temperature, and the heater set to hot.
Are you able to return the car to the seller for them to sort out the issue?
Kind regards,
Gareth.