What do you mean only atman is brahman, not you?

Atman means soul and brahman is spirit.

Realizing "I am Brahman" means engagement in spiritual activity because we are spirit, and our activities are exhibited even though we are contaminated by matter. To become Brahman does not mean to become void but to establish ourselves in the superior nature, which means superior energy and superior activities. To become Brahman means to be completely engaged in rendering devotional service to the Lord.