In July I am in Changchun and I want to visit Changbaishan, Heaven Lake and so on.

Take a bus to Erdaobaihe from Passenger Transport Center near Main Railway Station. The buses depart at 8:00 and 17:00, and the trip takes about 6 hours. Upon arrival, take a taxi to the mountain for about CNY 60.
For accommodation, you can stay at the foot of the mountain. The Days Inn Landscape Resort near the entrance is highly recommended. It costs CNY 700-1400 per night. You can dial at 86-0433-5052222 to book a room.