there no heat and no answer help me

Sounds like your A/C blower is bad. Is there any airflow?

Also check for air pockets in the cooling system.

Just a guess, but I'm thinking a worn water pump. If the impeller fins are worn enough, giving it too much space between the impeller and housing, it may not have enough flow at low idle. Coolant takes the path of least resistance, and the heater core passages provide enough resistance that most of the flow would be to the radiator. At higher speeds it would develop enough flow to push the coolant through the heater core.