Troubleshooting a Bosch ZWB28-3 combi boiler?

Currently it heats our hot water well but when cold is mixed in like in the shower the temperature of the water comming out of the showerhead is ever fluctuating....Also the heating function only works about half. The boiler fires and water is circulated through the radiators but it takes a long time for them to initially heat up and then it will only heat up the house to 62-63 degress even when the thermostat is set for 70.