跟你说拜拜对你说再见

This literally translates into 'Say Bye-Bye/Say Goodbye to You', emphasizing two forms - childlike (bye-bye) and formal (goodbye). It seems casual and friendly, maybe with slight sadness, indicating partings or endings. Perhaps it's reflecting the fact that despite having been so close before, they now must say farewell each other, symbolizing the departure or the separation after some interactions or relationships.