Vi kunne tage til stranden. Hvad siger du til det?

Yes—kunne is formally the past tense of kan (can), but in Danish it is also very commonly used to make a suggestion sound softer, more tentative, or more polite.

So Vi kunne tage til stranden is not really about the past. It means something like:

• We could go to the beach
• We might go to the beach
• How about going to the beach?

This is very similar to English, where could is often used for suggestions rather than past time.

Yes, you can, but it sounds a bit different.

• Vi kan tage til stranden = We can go to the beach
  This sounds more like talking about possibility or ability.
• Vi kunne tage til stranden = We could go to the beach
  This sounds more like a suggestion.

So if you are proposing an idea, kunne is often the more natural choice.

In Danish, tage literally means take, but it is also often used in expressions about going somewhere, especially in spoken language.

So:

• tage til stranden = go to the beach
• literally: take oneself to the beach

This is idiomatic Danish. English usually uses go, but Danish often uses tage in this kind of context.

You may also hear:

• Vi tager til Italien i morgen = We’re going to Italy tomorrow

So this is a normal pattern.

Til is used because it expresses movement toward a destination: to the beach.

Compare:

• Vi tager til stranden = we go to the beach
• Vi er på stranden = we are at/on the beach

This is a very useful contrast in Danish:

• til = motion toward a place
• på / i / ved etc. = location at a place

So til stranden is correct because the sentence is about going there.

Stranden is the definite form: the beach.

In Danish, the definite article is usually attached to the noun as an ending:

• en strand = a beach
• stranden = the beach

So til stranden means to the beach, not just to beach.

This is one of the basic patterns of Danish nouns.

Yes. In this sentence, vi means we, including both the speaker and the listener.

So Vi kunne tage til stranden means the speaker is suggesting that both of them go to the beach.

This is the normal interpretation unless context suggests otherwise.

Literally, it means:

• What say you to that?

But in natural English, it means something like:

• What do you think about that?
• How does that sound?
• What do you say to that?

It is an idiomatic way to ask for someone’s reaction to a suggestion.

Because Danish often uses sige til in this expression to ask for someone’s opinion or reaction to a proposal.

So:

• Hvad siger du til det? = What do you think about that? / How does that sound?

It does not focus on deep opinion in the abstract. It is usually about reacting to a suggestion that has just been made.

That makes it a very natural follow-up after Vi kunne tage til stranden.

Det refers to the whole idea or suggestion: going to the beach.

So:

• Hvad siger du til det? = What do you say to that idea?

Danish often uses det to refer back to an entire statement, situation, or proposal.

It is not referring to stranden specifically. It refers to the suggestion as a whole.

Not if you mean What do you think about that suggestion?

• Hvad siger du til det? = What do you think about that idea/proposal?
• Hvad siger du til stranden? = What do you think about the beach?

So changing det to stranden changes the meaning. Then you are asking about the beach itself, not about the suggestion of going there.

Danish main clauses usually follow verb-second word order.

In a question starting with a question word:

• Hvad = question word
• siger = verb
• du = subject

So the structure is:

• Hvad siger du til det?
• literally: What say you to that?

This is normal Danish question word order.

It is quite neutral and very common in everyday speech.

It can sound friendly and natural, especially after making a suggestion. It is neither especially formal nor rude.

You could use it with friends, family, coworkers, and in many ordinary situations.

A careful pronunciation would be something like:

• Vi → vee
• kunne → roughly KUN-uh, though the ending is very reduced
• tage → roughly TAY-uh
• til → often sounds like tel or a very reduced til
• stranden → roughly STRAN-nen, with the d usually not pronounced like a clear English d
• Hvad → often sounds more like va
• siger → roughly SEE-er or SI-er
• du → doo, often weakened in connected speech
• det → often like de

In real spoken Danish, many of these words are reduced. For example:

• Hvad is very often pronounced almost like va
• det is often pronounced almost like de

So the whole sentence may sound much smoother and less distinct than it looks in writing.

Yes, several. For example:

• Vi kan tage til stranden. Hvad siger du?
  = We can go to the beach. What do you say?

• Skal vi tage til stranden?
  = Shall we go to the beach?

• Hvad med at tage til stranden?
  = How about going to the beach?

These are all natural, but they have slightly different tones:

• Vi kunne ... = gentle suggestion
• Skal vi ...? = direct proposal
• Hvad med ...? = casual suggestion

So the original sentence is a very natural, polite, conversational way to make a suggestion.