Наша кошка иногда царапает диван, поэтому мы подстригаем ей когти.

Because наша has to agree with кошка in gender, number, and case.

• кошка is feminine singular
• so the possessive our must also be feminine singular: наша

Compare:

• наш кот = our male cat
• наша кошка = our female cat
• наши кошки = our cats

So наша кошка is the correct match.

Иногда means sometimes.

In this sentence:

• Наша кошка иногда царапает диван = Our cat sometimes scratches the sofa

Russian adverbs like иногда are fairly flexible in position. You can often move them without changing the basic meaning:

• Наша кошка иногда царапает диван
• Иногда наша кошка царапает диван
• Наша кошка царапает иногда диван — possible, but less natural here

The version in your sentence sounds normal and neutral.

Царапает is the 3rd person singular present-tense form of царапать = to scratch.

The subject is кошка = she / it, so Russian uses the he/she/it form:

• я царапаю = I scratch
• ты царапаешь = you scratch
• он / она царапает = he / she scratches
• мы царапаем = we scratch

So:

• кошка царапает = the cat scratches

It is in the accusative, but for an inanimate masculine singular noun, the accusative looks exactly like the nominative.

So:

• nominative: диван
• accusative: диван

That is why you do not see a change.

Compare with a feminine noun, where you often do see a difference:

• книга = book
• читать книгу = to read a book

So in царапает диван, диван is the direct object in the accusative, even though its form does not change.

Поэтому means therefore, that’s why, or so.

In this sentence:

• Наша кошка иногда царапает диван, поэтому мы подстригаем ей когти.
• Our cat sometimes scratches the sofa, so we trim her claws.

It introduces the result or consequence of the first clause.

Because this sentence has two clauses:

1. Наша кошка иногда царапает диван
2. поэтому мы подстригаем ей когти

Russian normally uses a comma before поэтому when it connects clauses like so / therefore.

So the punctuation here is standard.

Because Russian says this idea more like:

• we trim to her the claws

So ей is in the dative case, marking the person affected / the recipient.

Breakdown:

• мы подстригаем = we trim
• ей = to her
• когти = claws

English says we trim her claws, but Russian often uses:

• подстригать кому? = trim for/to whom?
• подстригать что? = trim what?

So:

• ей = dative
• когти = accusative

If you used её, that would usually mean her as a direct object, which is not the structure used here.

Когти is the accusative plural of коготь = claw.

Since the cat has more than one claw, Russian naturally uses the plural:

• коготь = claw
• когти = claws

For this noun, the accusative plural looks like the nominative plural, because it is inanimate:

• nominative plural: когти
• accusative plural: когти

So in the sentence, когти is the direct object: the thing being trimmed.

This is a very common Russian pattern with body parts, clothing, and things closely associated with a person.

Russian often prefers:

• мыли ему руки = washed his hands
• смотрела ему в глаза = looked into his eyes
• подстригаем ей когти = trim her claws

The logic is:

• ей tells you whose
• когти names the body part / associated thing

English usually uses a possessive adjective or pronoun:

• her claws

Russian often uses dative + body part/object instead.

Подстригать means to trim / clip / cut a bit, which fits claws, nails, hair, etc. very well.

• стричь is the more general verb to cut hair / shear / clip
• подстригать often suggests trimming neatly or cutting down a little

So подстригаем ей когти is a very natural way to say we trim her claws.

Also, подстригаем is imperfective, which works well here because this is a habitual/repeated action:

• the cat sometimes scratches the sofa
• so we regularly / from time to time trim her claws

Yes, but the meaning changes.

• мы подстригаем ей когти = we trim her claws / we are in the habit of trimming her claws
• мы подстрижём ей когти = we will trim her claws

The difference is aspect + tense:

• подстригаем = imperfective present, often habitual
• подстрижём = perfective future, one completed action in the future

In your sentence, the habitual meaning is the best fit.

No, Russian word order is fairly flexible, though some orders sound more natural than others.

The original sentence is neutral and natural:

• Наша кошка иногда царапает диван, поэтому мы подстригаем ей когти.

You could also say:

• Иногда наша кошка царапает диван, поэтому мы подстригаем ей когти.

That puts a bit more focus on sometimes.

You could move other elements too, but not every possible order sounds equally natural. Russian word order often changes focus rather than basic grammar.

Because Russian has no articles.

So:

• кошка can mean a cat or the cat
• диван can mean a sofa or the sofa
• когти can mean claws or the claws

The exact meaning depends on context.

In this sentence, English naturally uses our cat, the sofa, and her claws, but Russian does not need articles to express that.

The main stresses are:

• На́ша
• ко́шка
• иногда́
• цара́пает
• дива́н
• поэ́тому
• мы
• подстрига́ем
• ей
• ко́гти

A rough pronunciation guide:

• На́ша ко́шка иногда́ цара́пает дива́н, поэ́тому мы подстрига́ем ей ко́гти.

Stress matters in Russian, so it is worth learning words together with their stress.