Для школьного проекта она купила пластилин и мягкую глину, чтобы сделать маленькую фигурку.

Because для requires the genitive case.

So:

• школьный проект = a school project / the school project (dictionary form)
• для школьного проекта = for a school project / for the school project

Both words change because the adjective must agree with the noun:

• школьный → школьного
• проект → проекта

This is a very common pattern in Russian:

• для друга = for a friend
• для нового дома = for a new house
• для школьного проекта = for a school project

Для means for in the sense of intended purpose or meant for something.

So Для школьного проекта means:

• for a school project
• for the purpose of a school project

It tells us why she bought the materials.

Compare:

• Я купил это для мамы. = I bought this for Mom.
• Я купил это для работы. = I bought this for work.
• Она купила это для школьного проекта. = She bought it for a school project.

Yes, it could be omitted in many contexts.

Russian often leaves out subject pronouns when the subject is already clear from context. So both of these are possible:

• Она купила пластилин...
• Купила пластилин...

Including она can make the sentence clearer, more explicit, or slightly more natural if you are introducing the subject or contrasting her with someone else.

For example:

• Он купил бумагу, а она купила пластилин.
  = He bought paper, and she bought modeling clay.

So она is not grammatically strange here; it is just more explicit.

Because these are feminine singular nouns in the accusative case, used as direct objects.

The verbs купила and сделать both act on something:

• she bought what? → глину
• to make what? → фигурку

Dictionary forms:

• глина → глину
• фигурка → фигурку

This is a very common pattern for feminine nouns ending in -а:

• книга → книгу
• машина → машину
• глина → глину
• фигурка → фигурку

Because пластилин is a masculine inanimate noun, and in Russian the accusative singular of masculine inanimate nouns is usually the same as the nominative.

So:

• пластилин (nominative)
• пластилин (accusative)

But глина is feminine, so it changes:

• глина (nominative)
• глину (accusative)

That is why you get:

• купила пластилин
• купила глину

This is one of the most important case patterns to get used to in Russian.

Because the adjective must agree with the noun in gender, number, and case.

The noun глина is:

• feminine
• singular
• accusative

So the adjective мягкий has to match that:

• мягкий → masculine nominative
• мягкая → feminine nominative
• мягкую → feminine accusative

So:

• мягкая глина = soft clay
• купила мягкую глину = bought soft clay

The same thing happens with маленькую фигурку:

• маленькая фигурка → nominative
• сделать маленькую фигурку → accusative

They are related materials, but not the same thing.

• пластилин = modeling clay / plasticine
  Usually a soft synthetic material used by children or artists for shaping.
• глина = clay
  More literally clay, the natural material.

So the sentence says she bought plasticine and soft clay, meaning two different sculpting materials.

A learner should notice that Russian often uses specific material words in ways that do not map perfectly onto one English word. In context, пластилин is typically the children’s modeling material.

Купила is the past tense of купить = to buy.

The ending -а shows that the subject is feminine singular.

Compare:

• он купил = he bought
• она купила = she bought
• оно купило = it bought
• они купили = they bought

So the verb agrees with the gender and number of the subject in the past tense.

Since the subject is она, the correct form is купила.

Because купила is perfective, and here the sentence describes a completed action: she went and bought the materials.

• купить = perfective, to buy / to purchase successfully, as a completed event
• покупать = imperfective, to buy / be buying / buy regularly

In this sentence, the completed result matters: she obtained the materials for the project.

So:

• она купила пластилин = she bought modeling clay
• она покупала пластилин = she was buying / used to buy / bought (with focus on process or repetition, depending on context)

Perfective is very natural here.

Чтобы introduces a purpose clause: in order to / so that.

So:

• чтобы сделать маленькую фигурку = in order to make a small figurine

This is one of the most common ways to express purpose in Russian.

Examples:

• Я пришёл, чтобы помочь. = I came to help.
• Она открыла окно, чтобы проветрить комнату. = She opened the window to air out the room.
• Она купила пластилин, чтобы сделать фигурку. = She bought modeling clay to make a figurine.

Because the subject is the same person, Russian commonly uses чтобы + infinitive.

Because сделать is perfective, and it focuses on the finished result: making a figurine successfully.

• делать = to do / to make, imperfective
• сделать = to do / to make, perfective

Here the idea is not just the process of working on it, but the goal of producing a completed figurine.

So:

• чтобы сделать маленькую фигурку = in order to make a small figurine, with the result in mind

If you used чтобы делать, it would usually suggest an ongoing or repeated activity, which does not fit as well here.

Фигурка is a diminutive form, and it usually means a small figure, figurine, or little shaped object.

• фигура = figure, shape, sometimes a person’s figure
• фигурка = little figure, figurine

So маленькую фигурку sounds very natural for something small made from clay or plasticine.

Russian uses diminutives very often, not only for affection, but also simply for something small or neat in size.

A little bit, but it is still perfectly natural.

You are right that фигурка already suggests something small. But adding маленькую can still:

• emphasize the size
• make the image more vivid
• sound natural in everyday speech

So фигурку already leans toward figurine, and маленькую фигурку means something like a small little figurine. In English that may feel slightly repetitive, but in Russian it sounds normal.

Russian word order is fairly flexible, though not completely random.

The given sentence is neutral and natural:

• Для школьного проекта она купила пластилин и мягкую глину, чтобы сделать маленькую фигурку.

But you could also say:

• Она купила пластилин и мягкую глину для школьного проекта, чтобы сделать маленькую фигурку.
• Пластилин и мягкую глину она купила для школьного проекта, чтобы сделать маленькую фигурку.

The meaning stays close, but the emphasis changes:

• putting Для школьного проекта first highlights the purpose/context
• putting пластилин и мягкую глину first highlights what she bought

So Russian word order often helps manage focus and emphasis.

It can mean either, depending on context.

Russian has no articles, so it does not directly mark the difference between a and the.

So:

• для школьного проекта can mean for a school project
• or for the school project

You decide from the situation:

• if the project is being mentioned for the first time, English often uses a
• if both speaker and listener already know which project, English often uses the

This is one of the most common things English speakers need to get used to in Russian: article meanings are usually understood from context rather than from separate words.

Yes.

In this sentence, чтобы is followed by the infinitive сделать because the subject is the same person: she bought the materials so that she could make a figurine.

But Russian can also use чтобы with a finite verb, especially when the subject is different or when the clause is more fully expressed.

For example:

• Я позвонил, чтобы она пришла.
  = I called so that she would come.

So:

• same subject often → чтобы + infinitive
• different subject often → чтобы + past-tense-like verb form

In your sentence, чтобы сделать is the natural choice.