One way to express disbelief about something that is happening, has happened or will happen in Spanish is by forming a question introduced by "que".
It is important to note that this "que" does not have an accent despite being a question.
Have a look and listen to the following examples:
¿Que te vas a casar con Javier? No lo puedo creer.Are you really marrying Javier? I can't believe it.
¿Que escalásteis el Kilimanjaro? Increible.I can't believe you climbed Kilimanjaro! Incredible!
¿Que tu hija va a salir en la tele?Your daughter is going to be on TV?
Que without an accent
In this case "que" is a conjunction, although in this specific usage it is as though part of the sentence is omitted.
Let's look at the following example to understand how the word "que" works in this sort of sentence to express surprise and disbelief about something you have been told or have heard generally:
¿Que te ha tocado la lotería?You've really won the lottery?
We could easily have said the same in a exclamatory sentence:
¡No puedo creer que te haya tocado la lotería!
I can't believe that you won the lottery!
¡Me han dicho que te ha tocado la lotería!
I've been told that you won the lottery!
But with the shortened "que" version, the initial phrase that expresses surprise/disbelief is omitted.
Important note about using the subjunctive
Bear in mind that this structure does not admit the subjunctive if the initial sentence is in the indicative.
For example, if you imagine that someone says: "Tengo mucho frío", you could reply: "¿Que tienes mucho frío?" but not "¿Que tengas mucho frío?"
However, look at this example where the initial sentence is in the subjunctive already to express disbelief:
"Me pidió que le diera dinero." (subjunctive)
then the reply would be:
"¿Que le dieras dinero?" (subjunctive)
You can review the other uses of "qué" with and "que" without a written accent here: Difference between qué and que (with and without an accent)
¿Que te vas a casar con Javier? No lo puedo creer.Are you really marrying Javier? I can't believe it. ¿Que tu hija va a salir en la tele?Your daughter is going to be on TV? ¿Que te ha tocado la lotería?You've really won the lottery? ¿Que escalásteis el Kilimanjaro? Increible.I can't believe you climbed Kilimanjaro! Incredible!