Learn Hardcore Swedish: Jag har en idé: vi går till skogen och lämnar mobilen hemma. - I have an idea: we go to the forest and leave the mobile phone at home.

Jag har en idé = I have an idea (I possess an idea right now).
Jag får en idé = I get an idea (the idea is just coming to me at this moment).

In everyday speech, when you want to propose something, you almost always say Jag har en idé (just like English I have an idea), not Jag får en idé.

What is the function of the colon ":" after "Jag har en idé"?

The colon introduces what the idea actually is. It works very similarly to English:

Jag har en idé: vi går till skogen …
= I have an idea: we go to the forest …

In Swedish, a colon is commonly used to introduce:

an explanation or elaboration (like here)
direct speech
lists

So the structure is: statement + : + explanation/idea/quote.

Why is it "vi går" (present tense) when it’s a suggestion about the future? Shouldn’t it be something like "vi ska gå"?

Swedish often uses the present tense for:

near‑future plans
suggestions/proposals

So Vi går till skogen can mean Let’s go to the forest or We’ll go to the forest, depending on context and tone.

You can say Vi ska gå till skogen (= We are going to go to the forest), but in a suggestion like this, simple present vi går is very natural and sounds more like let’s go.

Is "vi går till skogen" the normal way to say "let’s go to the forest" in Swedish?

Yes. There are a few common ways:

Vi går till skogen. – very usual; in context it means Let’s go to the forest.
Ska vi gå till skogen? – literally Shall we go to the forest?; also a typical suggestion.
Kom, så går vi till skogen. – Come, let’s go to the forest.

In your sentence, Vi går till skogen is understood as a friendly suggestion.

Why is it "till skogen" and not "i skogen"?

Because you are talking about movement to a place:

till = to (movement towards a destination)
i = in / inside

So:

Vi går till skogen. = We go to the forest.
Vi är i skogen. = We are in the forest.

If you changed it to i skogen, it would sound like you’re already inside the forest: we walk in the forest (not to it).

Why is it "skogen" with -en at the end? What does that ending mean?

The -en ending is the definite article (“the”) attached to the noun:

en skog = a forest
skogen = the forest

Swedish usually puts the at the end of the noun as a suffix instead of as a separate word.

en mobil → mobilen (a phone → the phone)
en idé → idén (an idea → the idea)
en skog → skogen (a forest → the forest)

Could I say "till en skog" instead of "till skogen"? What would be the difference?

Yes, but it changes the meaning slightly:

Vi går till skogen.
= We go to the forest (a specific forest that we both know or have in mind).
Vi går till en skog.
= We go to a forest (some forest, not specified which one; more abstract or less specific).

In everyday speech, till skogen is more natural if you mean “to the forest (we usually go to / that’s nearby)”.

Why is it "mobilen" and not just "mobil"?

Again, it’s the definite ending -en:

en mobil = a mobile phone
mobilen = the mobile phone / the phone

In context, lämnar mobilen hemma means leave the (our) phone at home.
Using mobil without -en would sound like leave a phone at home, which is not what you want here.

Is "mobilen" the same as "mobiltelefonen" or "cell phone"?

Yes, in everyday Swedish:

en mobil / mobilen = (mobile) phone, cell phone
en mobiltelefon / mobiltelefonen = more formal/technical, but means the same thing.

In normal conversation people almost always say mobil or mobilen, just like English speakers say phone rather than mobile telephone.

What’s the difference between "hemma" and "hem"?

They’re related but used differently:

hemma = at home (location)
hem = home / (to) home (direction or more abstract)

Examples:

Jag är hemma. – I am at home.
Jag går hem. – I’m going home.
Lämna mobilen hemma. – Leave the phone at home.

So in your sentence, hemma is correct because it’s about the phone’s location: at home.

Why is the verb order "vi går till skogen och lämnar mobilen hemma"? Could I say "vi går till skogen och vi lämnar mobilen hemma"?

Both are correct:

Vi går till skogen och lämnar mobilen hemma.
Vi går till skogen och vi lämnar mobilen hemma.

In the second part, Swedish often drops the repeated subject vi if it’s the same as in the first part, so the shorter version is more common.

The important point is that in each clause the verb comes in the second position (the V2 rule):

Vi (1) går (2) till skogen …
(vi) lämnar (2) mobilen hemma …

How would I say “not go to the forest” or “not leave the phone at home” using this sentence?

Use inte (not) after the verb:

Vi går inte till skogen. – We’re not going to the forest.
Vi lämnar inte mobilen hemma. – We’re not leaving the phone at home.

So your full sentence with negation could be, for example:

Jag har en idé: vi går inte till skogen och vi lämnar inte mobilen hemma.
= I have an idea: we don’t go to the forest and we don’t leave the phone at home.

How do you pronounce "idé", and why does it have an accent on é?

Idé is pronounced approximately like:

[i‑DEH] (IPA: /iˈdeː/)

The accent é:

marks the vowel as a long /eː/ sound
helps show the stress is on the second syllable: i‑dé

It’s a loanword from French, and many such words keep the accent in Swedish (e.g. idé, kafé, armé).