How to place a sell order on Kraken that only sells when the price stops going up?
At the moment, Kraken has disabled all advanced order types - so there is nothing that can do what you're looking for on Kraken.

That said, I think the order type that you are looking for is called trailing-stop-order.
You can read more about it here, for example: https://support.bitfinex.com/hc/en-us/articles/115003506545-Trailing-Stop-Order