Vi flytter leirgodset med en gang tørketiden er over.

Here it means as soon as.

So:

• med en gang
  • clause = as soon as
• med en gang! on its own often means immediately / right away

In this sentence, it introduces a time clause:

• med en gang tørketiden er over = as soon as the drying time is over

So even though the words literally look like with one time, that is not how you should understand it.

Because Norwegian often uses the present tense for future events when the timing is clear from the context.

So:

• Vi flytter ... can mean We are moving / We move / We will move ...
• ... tørketiden er over literally uses present tense too, even though in English we also often do this in time clauses: as soon as the drying time is over

This is very normal in Norwegian. You do not need skal here.

Compare:

• Vi flytter leirgodset i morgen. = We’re moving the earthenware tomorrow.
• Vi skal flytte leirgodset i morgen. = We’re going to move the earthenware tomorrow.

Both are possible, but the simple present is very common.

Leirgodset is the definite form of leirgods, a compound noun.

In this context, it means something like:

• the earthenware
• the clay goods
• the clay items

This is probably about pottery or ceramic items that need time to dry.

A learner might mistake leir for camp, but here the word is part of leirgods, which refers to clay/earthenware, not camping equipment.

Because Norwegian usually puts definiteness at the end of the noun.

So:

• tørketid = drying time
• tørketiden = the drying time

and

• leirgods = earthenware / clay goods
• leirgodset = the earthenware / the clay goods

This is one of the biggest differences from English. Instead of saying the drying time, Norwegian often says drying-time-the.

It literally means the drying time is over.

A few useful points:

• tørketid = drying time
• -en makes it definite: tørketiden = the drying time
• er over = is over / has ended / is finished

So the whole clause means:

• tørketiden er over = the drying time is over

This is a very common Norwegian pattern:

• ferien er over = the holiday is over
• møtet er over = the meeting is over
• ventetiden er over = the waiting time is over

Because med en gang already introduces the time clause.

So:

• med en gang tørketiden er over = as soon as the drying time is over

You do not need an extra når here.

Think of med en gang as functioning like a multi-word conjunction in this sentence.

Yes. You can put the time clause first:

• Med en gang tørketiden er over, flytter vi leirgodset.

That means the same thing.

But notice the word order in the main clause:

• Vi flytter leirgodset ...
• Med en gang tørketiden er over, flytter vi leirgodset.

When the time expression comes first, Norwegian uses normal V2 word order, so the verb comes before the subject in the main clause:

• flytter vi, not vi flytter

That is a very important Norwegian pattern.

Grammatically, it is singular definite.

But semantically, it can refer to a collection or material rather than one single object. That is why English might translate it as:

• the earthenware
• the clay goods
• the clay items

So it behaves a bit like a mass or collective noun.

This kind of mismatch is normal across languages: a word can be singular in grammar but refer to multiple things in meaning.

Because leirgods is not being treated here as a regular countable plural noun meaning separate individual items. It is being used as a collective/material noun.

So:

• leirgods = earthenware / clay goods
• leirgodset = the earthenware

If you wanted to talk about individual objects, Norwegian would often choose a different noun altogether, depending on context, such as gjenstander, ting, krukker, kopper, and so on.

Sometimes, but they are not exactly the same.

• med en gang = as soon as
• straks can also mean immediately / as soon as, but the tone may be slightly different
• når = when, which can be more neutral and less immediate

Compare:

• Vi flytter leirgodset med en gang tørketiden er over.
  = We move it as soon as the drying time is over.

• Vi flytter leirgodset når tørketiden er over.
  = We move it when the drying time is over.

The second version is understandable, but med en gang more clearly emphasizes immediately after the drying time ends.