After Effects Timeline not work smoothly

No one will be able to help you unless you provide a much more detailed question.

What do you mean by the Timeline does not work smoothly.

A general note on preview in AE is that it builds a preview in RAm and then can play that preview back for you. The geen line indicates that this section of the timeline is in RAM and ready to playback. The grey area is the range that has not been previewed in RAm yet. 

Cuál es la razón por la que dices que After Effects tiene problemas, intenta explicar lo que está sucendiendo.