Problem with smooth object rotation - Rinterp

Hello! I’m trying to do simple OFF and ON lamp switch but I thought that ceiling fan should slowly stop and start rotating when Player switch the light. I can’t figure out how to achieve this. Screenshot shows where I’m right now and there are some problems.

When level starts fan is spining like crazy but after I press button he acts as I want. There is also problem with clicking too fast…

Here is a link to the movie:

What am I doing wrong? Is there simple solution ? Maybe different method ?

Thanks!