atarasii heya ni au kagu wo sukosizutu kau tumori desu.

Because 新しい is an i-adjective, and in Japanese, adjectives usually come directly before the noun they modify.

So:

• 新しい部屋 = a new room

This works much like English in this case.

With the verb 合う, the thing that something matches, fits, or suits is often marked with に.

So:

• 部屋に合う = to match the room
• more literally: to suit the room

This may feel different from English, because English often uses match with a direct object, but Japanese commonly uses に here.

Here, 合う means something like:

• to match
• to suit
• to fit well with

So 部屋に合う家具 means:

• furniture that matches the room
• furniture that suits the room

It does not mean physically fitting inside the room in a strict size sense only, though it can sometimes have that kind of nuance depending on context. Here it most naturally means matching the style, feeling, or look of the new room.

Because Japanese uses a relative clause before the noun it modifies.

So:

• 部屋に合う家具 = furniture that matches the room

In English, the noun comes first and the descriptive clause comes after it:

• furniture that matches the room

In Japanese, the whole descriptive part comes first:

• [部屋に合う] 家具

This is a very common Japanese structure.

Japanese does not need a separate word like that, which, or who in relative clauses.

English:

• furniture that matches the room

Japanese:

• 部屋に合う家具

The verb phrase directly attaches to the noun. So Japanese often expresses this idea more compactly than English.

少しずつ means:

• little by little
• bit by bit
• gradually
• in small amounts at a time

So it suggests buying the furniture over time, not all at once.

By contrast, 少し by itself usually just means:

• a little
• a small amount

So:

• 少し買う = buy a little
• 少しずつ買う = buy little by little

The ずつ adds the idea of repeated small amounts.

Because つもりです attaches to the dictionary/plain form of the verb.

So the correct pattern is:

• 買うつもりです = intend to buy / plan to buy

Not:

• 買いますつもりです ❌

This is a standard grammar pattern:

• verb plain form + つもりです

Examples:

• 行くつもりです = I intend to go
• 勉強するつもりです = I intend to study

つもりです expresses intention or a plan in the speaker’s mind.

So 買うつもりです means:

• I intend to buy
• I’m planning to buy

It often sounds a little more personal and intention-based than just stating a schedule.

Because the sentence ends with です, and in Japanese, the final part of the sentence often determines the politeness level.

Here:

• 合う is inside a modifying clause
• 買う is part of the grammar pattern 買うつもりです

So even though those verbs are plain form, the overall sentence is polite because it ends with つもりです.

This is very normal in Japanese.

The subject is omitted, which is extremely common in Japanese.

So the sentence could mean:

• I plan to buy...
• We plan to buy...
• sometimes even They plan to buy...

depending on context.

In many everyday situations, if someone says this by itself, the most natural assumption is:

• I plan to buy furniture little by little that matches the new room.

Japanese often leaves out information that is already understood.

Because 家具 is the direct object of 買う.

So:

• 家具を買う = buy furniture

Even though 家具 is modified by the clause 新しい部屋に合う, it is still the thing being bought, so it takes を.

Structure:

• [新しい部屋に合う] 家具 を 買う
• buy [furniture that matches the new room]

It modifies 部屋, not 家具.

So the structure is:

• 新しい部屋 = new room
• 新しい部屋に合う家具 = furniture that matches the new room

If you wanted to say new furniture, you would say:

• 新しい家具

So this sentence is about furniture for a new room, not necessarily new furniture.

A helpful breakdown is:

• 新しい部屋に合う = that matches the new room
• 家具を = furniture
• 少しずつ = little by little
• 買うつもりです = intend to buy

So the sentence structure is:

• [新しい部屋に合う] 家具を 少しずつ 買うつもりです。

Or more literally:

• As for furniture that matches the new room, I intend to buy it little by little.

This kind of noun-modifying clause is one of the most important patterns in Japanese.

Yes, to some extent. Japanese word order is more flexible than English, especially with adverbs like 少しずつ.

For example, these are both natural:

• 新しい部屋に合う家具を少しずつ買うつもりです。
• 新しい部屋に合う家具を買うつもりです、少しずつ。
  (possible, but less neutral in ordinary written form)

The most standard order here is the original one, with 少しずつ placed before 買う because it modifies the action of buying.

So the given sentence is the most natural neutral version.