Ravana is not alive?

No, Ravana is not alive. In the Ramayana, Ravana was killed by Rama using a Brahma's weapon given to him by Sage Agastya.

However, some people believe that Ravana's body is still alive and may come back to life. According to local legends, Ravana's body is kept in a cave in the Muwara Eliya forests of Sri Lanka. The cave is said to be located in Ragla, about 73 km from Ella. Some say that Ravana's body is mummified and kept in a casket that is 18 ft long and 5 ft wide. Others say that a special coating keeps Ravana's body well-preserved. Some also believe that the Nagakul people and other animals guard the cave.