Don't confuse "will" (desire, wish) with "will" (intend, future tense auxiliary) and "have" (own, possess) with "have" (past tense auxiliary).
"I will have returned" is future-perfect tense (an action in the future that will complete), but 'vil ha' is "want (will) to have (possess)".
I'm wondering why De vil ha iskrem, can mean both - They want ice-cream and They will have ice-cream?
The latter is a literal translation and would be wrong if you want to translate the intended meaning. "vil ha" should always be translated to "want" afaik.
What if you wanted to say They will get/have icecream? asking because google translate says ønsker as wants but then if I do the back to english thing it says wishes.
In English, or at least in the US, it is pretty common for someone to say "I/we/they will have ice cream" as way of saying they want it. This is usually limited to food I think.
What I understood is that "vil ha" is "to want something" and that "vil" is "to want to DO something". Am I wrong? Am I right? But I never seen/understood it as "will have"...
It is always "vil du ha" when it is a question and always "du vil ha" if it is a statement, because of the word order.
I know that I'm probably getting ahead of the course now, but can "vil" be used when froming future tense in norwegian? If yes, can someone give an example of that?
Yes, the future tense is formed with "skal" and "vil" (and also "kommer til å", which means "going to").
"Vil" is used in situations when the subject has no control over the events.
Would "De vil iskrem" be correct to say as well if you want to say "they want ice-cream"?
"Vil" is a modal auxiliary verb, so it cannot be the main verb of a sentence.
If what they want is expressed by a noun, you need to add the verb "ha" after "vil". If what they want is expressed with a verb, then that verb takes the role of main verb in the sentence:
"De vil ha iskrem."
"De vil spise (iskrem)."
I would think so. But I translated as "they want to have ice cream" and this was rejected, and corrected to "they want ice cream". This may be because English is not my native language. I got the concept right, but possibly the sentence with "to have" added is incorrect English.
I also wrote 'they want to have ice cream' (also rejected). Maybe it is more British English? I don't know, how about you?
"Iskrem" just sounds better than Swedish "glass" which stems from French "glacé".