How to change in a certain period of time the speed of the animation?

Good time of day. There is an animation:
.s {animation: ssline 12s; transition-timing-function: ease-out; }

In ssline is just 2 keyframes, the start height and end height. The challenge is this:
How to leave the animation speed ease-out and at the same time in two places insert the two short period in which the speed will be greatly increased (in 5 times)? That is, the animation is standard with the ease-out and say, 6 seconds and 8 seconds the speed increases for a half a second and then comes back to normal
June 8th 19 at 17:18
1 answer
June 8th 19 at 17:20
https://webref.ru/css/keyframes
Examine this article. Good luck

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