Learn Dutch: Het is belangrijk om de receptie te bellen over de airconditioning. - It is important to call the reception about the air conditioning.

We use the om ... te construction after adjectives like belangrijk (important) to express "It is [adjective] to [do something]". It connects the main phrase Het is belangrijk with the infinitive verb phrase de receptie te bellen.

Why is over de airconditioning placed at the very end, after the verb te bellen?

In Dutch, verbs usually get pushed to the end of a clause. However, prepositional phrases like over de airconditioning are an exception. They can be placed after the final verb to prevent the middle of the sentence from becoming too long and heavy. You could also perfectly say om de receptie over de airconditioning te bellen.

How could I expand this sentence using the current lesson's conjunction in plaats van dat?

You can use in plaats van dat (instead of) to add a contrasting action with a new subject. For example: Het is belangrijk om de receptie te bellen, in plaats van dat we het zelf repareren (It is important to call the reception, instead of us fixing it ourselves). Notice that in plaats van dat acts as a subordinating conjunction and sends the verb repareren to the end of its clause!

Is the English word airconditioning standard in Dutch?