Unser Rateversuch liegt zwar daneben, aber die Erklärung passt.

Because Rateversuch is masculine singular and it is the subject of the sentence, so it is in the nominative case.

The possessive determiner unser- behaves a bit like ein-. In the nominative masculine singular, it usually has no ending:

• unser Rateversuch
• mein Bruder
• dein Hund

Compare:

• unsere Erklärung → feminine singular nominative
• unser Kind → neuter singular nominative
• unsere Versuche → plural nominative

So unser here is simply the correct masculine nominative form.

Rateversuch is a compound noun made from:

• raten = to guess
• der Versuch = attempt, try

So der Rateversuch means something like:

• guessing attempt
• attempt to guess
• our guess

It is understandable and natural enough, especially in contexts where someone is trying to work something out. But in everyday German, depending on the situation, speakers might also use words like:

• Vermutung = assumption, guess
• Tipp = guess, tip
• Erklärungsversuch = attempt at an explanation

So Rateversuch is valid and clear, but it is a bit more explicitly built-up than the most common everyday choice.

zwar ... aber is a very common pattern meaning something like:

• admittedly ... but
• it is true that ... but
• yes ... but

It introduces a contrast. The first part concedes something, and the second part gives the more important counterpoint.

In your sentence:

• Unser Rateversuch liegt zwar daneben, aber die Erklärung passt.

This means roughly:

• Our guess may be wrong, but the explanation fits.

A few more examples:

• Er ist zwar müde, aber er arbeitet weiter.
  He is tired, but he keeps working.

• Das ist zwar teuer, aber gut.
  It is expensive, but good.

So zwar signals a concession, and aber introduces the contrast.

Because zwar does not have to stand first. Very often it appears in the middle field of the clause, after the finite verb:

• Unser Rateversuch liegt zwar daneben ...

That is completely normal.

You can also put zwar earlier for emphasis:

• Zwar liegt unser Rateversuch daneben, aber die Erklärung passt.

Both are grammatical. The version with zwar in the middle is often the more neutral-sounding one.

The important thing is the overall zwar ... aber relationship, not that zwar must come first.

Literally, daneben often means next to it or beside it.

But in this sentence it is being used idiomatically. With liegen, it forms the expression danebenliegen, which means:

• to be wrong
• to be off
• to be off the mark

So:

• Unser Rateversuch liegt daneben.
  = Our guess is wrong.

This is a very common figurative use.

Compare the two meanings:

• Das Glas steht daneben.
  = The glass is standing next to it.
  literal

• Mit deiner Vermutung liegst du daneben.
  = Your assumption is wrong.
  idiomatic

That is because danebenliegen is an idiomatic expression.

German often uses verbs in ways that are not translated literally into English. Here, liegen is part of a fixed idea:

• richtig liegen = to be correct
• falsch liegen = to be mistaken
• danebenliegen = to be wrong / off the mark

So German treats correctness almost like a position: something can lie right or lie beside the correct point.

Examples:

• Du liegst richtig.
  = You are right.

• Ich lag falsch.
  = I was wrong.

• Wir liegen völlig daneben.
  = We are completely wrong.

So the verb choice is idiomatic, not literal.

It is best thought of as the separable verb danebenliegen.

In a finite main clause, separable verbs split:

• Unser Rateversuch liegt zwar daneben.

In the infinitive or at the end of a clause, they stay together:

• Unser Rateversuch scheint danebenzuliegen.
• ..., weil unser Rateversuch danebenliegt.

So learners often meet it in two shapes:

• split in main clauses
• together in infinitives and clause-final positions

That is normal for separable verbs in German.

The verb passen literally means to fit. But like English fit, it can be used in several ways.

Here die Erklärung passt means something like:

• the explanation fits
• the explanation makes sense
• the explanation matches the situation

It does not mean that the explanation physically fits somewhere. It means it is the right explanation or it is consistent with the facts.

Other uses of passen:

• Das Hemd passt mir.
  = The shirt fits me.

• Das passt gut zusammen.
  = That goes well together.

• Die Antwort passt nicht zur Frage.
  = The answer does not fit the question.

So in your sentence, passt is being used in a more abstract sense.

Because aber is a coordinating conjunction, and after it the following clause keeps normal main-clause word order.

In a German main clause, the finite verb is in second position:

• Die Erklärung passt.

When you add aber, that does not change the rule:

• ..., aber die Erklärung passt.

The conjunction aber does not take up the first position of the clause in the same way an adverb would. It simply links two main clauses.

Compare:

• Die Erklärung passt.
• Aber die Erklärung passt.

Both keep normal main-clause order.

If you said aber passt die Erklärung, that would sound like a yes/no question pattern or a marked structure, not the normal statement here.

Yes, absolutely.

That would be a very natural alternative. Vermutung is often more common in everyday German than Rateversuch, depending on the context.

The meaning shifts slightly:

• Rateversuch emphasizes the act of trying to guess
• Vermutung emphasizes the assumption/guess itself

Both work well. Native speakers often choose whichever sounds more natural for the situation.

Yes. Erklärung is a feminine noun, so its nominative singular article is die:

• die Erklärung

In this clause, die Erklärung is the subject of passt, so nominative is correct.

This is just the normal dictionary gender of the noun:

• der Versuch
• die Erklärung
• das Kind

So die here is not special for this sentence; it is simply the normal feminine article.

The sentence has two coordinated main clauses:

1. Unser Rateversuch liegt zwar daneben
2. aber die Erklärung passt

Structure of the first clause:

• Unser Rateversuch = subject
• liegt = finite verb
• zwar = concessive particle
• daneben = separable prefix part / adverb in the idiom danebenliegen

Structure of the second clause:

• aber = coordinating conjunction
• die Erklärung = subject
• passt = finite verb

So the whole sentence is built as:

• main clause + aber + main clause

That is why it feels compact and balanced.