How can i wait until the tween is completed or when the Main Part goes inside another part?

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2

I assume you mean the TweenRocket tween?

If so:

TweenRocket:Play()
TweenRocket.Completed:Wait()

This will make the tween wait until its completed, completed being an event, and by using the :Wait() after it, we can make it wait till its completed.

Probably a bad explanation but thats how it works!