Я не знаю, какая у нашей собаки порода, но все говорят, что она очень умная.

In Russian, the present-tense verb to be is usually omitted.

So:

• какая у нашей собаки порода = what breed our dog is
• она очень умная = she is very smart

Russian does not normally say есть here. The idea of is is understood from the structure.

Because какая agrees with порода, and порода is a feminine singular noun.

So the pattern is:

• masculine: какой
• feminine: какая
• neuter: какое
• plural: какие

Here the speaker is asking about порода, so the feminine form какая is required.

Because порода is not the direct object of знаю here.

The sentence is not structured as I don’t know the breed. Instead, it is I don’t know what breed our dog is. That second part is an indirect question, and inside that indirect question, порода is the noun being described by какая.

So:

• Я не знаю породу = I don’t know the breed (direct object)
• Я не знаю, какая у нашей собаки порода = I don’t know what breed our dog is (indirect question)

У + genitive is a very common Russian way to show possession or association.

So у нашей собаки literally means something like of our dog / with our dog / belonging to our dog, depending on context. In this sentence, it means our dog’s in a natural Russian way.

That is why собака changes to собаки and наша changes to нашей: both are in the genitive after у.

Yes. Russian has more than one natural way to say this idea.

Very common alternatives are:

• Я не знаю, какая порода у нашей собаки.
• Я не знаю, какой породы наша собака.

All of these are natural. The version in your sentence is fine, but какая порода у нашей собаки may sound a bit more straightforward to many learners because the noun порода comes earlier.

Russian word order is more flexible than English word order because Russian uses case endings to show grammatical relationships.

English depends heavily on word order, but Russian can move words around for emphasis, rhythm, or style.

So these can all be possible with slightly different focus:

• какая у нашей собаки порода
• какая порода у нашей собаки

The meaning stays basically the same, but the emphasis shifts a little.

Because this is an indirect question, not a direct question.

The whole sentence is a statement:

• I don’t know ... but everyone says ...

So Russian writes it as a normal declarative sentence with commas, not with a question mark inside it.

If it were a direct question, you would write:

• Какая у нашей собаки порода?

Because собака is a feminine noun in Russian, so pronouns and adjectives usually agree with its grammatical gender.

That is why you get:

• наша собака
• она
• умная

Even if the dog is biologically male, speakers often still use feminine forms with собака because the noun itself is feminine. If they want masculine agreement, they may use a different noun such as пёс or use the dog’s name.

Умная agrees with она / собака, which are feminine singular.

So the adjective must also be feminine singular:

• masculine: умный
• feminine: умная
• neuter: умное
• plural: умные

Also, this is the full adjective form, which is the normal everyday way to say smart here.

You can say она умна, but it sounds more literary, formal, or stylistically marked.

In normal everyday speech, Russian usually prefers the full form here:

• она очень умная

So for most learners, умная is the form to expect in ordinary conversation.

Because все here means everyone / all people, and it takes a plural verb.

So:

• все говорят = everyone says / all people say

Do not confuse it with всё (with ё), which means everything and would take singular neuter agreement:

• всё говорит = everything says or everything indicates

In your sentence, it is clearly all people, so говорят is correct.

Here что means that and introduces a subordinate clause.

So:

• все говорят, что она очень умная = everyone says that she is very smart

This что is not the question word what in this sentence. It is a conjunction linking the two parts of the sentence.

Russian uses commas before:

• но = but
• что when it introduces a subordinate clause
• an indirect-question clause after something like я не знаю

So the commas separate the sentence into its logical parts:

• Я не знаю, ...
• но ...
• ..., что ...

Russian punctuation is generally stricter than English punctuation in this kind of sentence, so these commas are required.