I suspect you don’t understand how the different flow cards (If / And / Then) and logic cards work.
The flow card Maximum temperature kleiner… is a If/When or Trigger card. This card starts this flow when the max. day temperature drops below 18 °C. And only then this card is triggered and the flow is started. So it’s not a condition card (And).
An ALL card after a trigger card (If/When) never works, please have a look at this topic.
What you need is a trigger, that recognizes when you start showering, e.g. a humidity sensor or a switch button. Then turn on ventilator. And (condition card) max. day temperature is below 18 °C then turn the heater on. The condition card can be a card from the app, but usually logic cards inkl. tags must be used. Perhaps this support article will help you to understand it.
If you need further help, please let us know.
