Changing speed of animation depending on index

[mazc23]

Good night, im stuck on an animation, the thing is , i have three lines paragraph, and they transalte in the animation from english to spanish, and the client wants, the english paragraph stays in english 15 seconds, and 4 seconds in spanish, and keep doing it in a loop, i only had achieved to change three times but then the animation stops. Can anyone help me? thanks