kongetu no uti ni atarasii heya wo kimetai desu.

It means by the end of this month or while it is still this month.

The nuance is not just in this month in a general sense. It emphasizes finishing something before the month changes.

So 今月のうちに feels like:

• sometime before this month ends
• while there is still time left in this month

Noun + のうちに is a common pattern.

Here, うち means something like within, during, or before the situation changes.

So:

• 今月 = this month
• 今月のうちに = within this month / before this month is over

This pattern is often used when there is a limited time window:

• 夏のうちに = during the summer / before summer ends
• 若いうちに = while you are young
• 熱いうちに = while it is still hot

Yes. 今月中に is very natural and very common.

Both mean roughly by the end of this month, but there is a slight nuance:

• 今月中に = by the end of this month
• 今月のうちに = while it is still this month / before this month is over

In many situations, they are interchangeable.
If you are talking about apartment hunting, 今月中に新しい部屋を決めたいです would sound very normal.

Yes, 部屋 literally means room. But in real Japanese, especially when talking about renting or moving, 部屋 is often used more broadly for a rental room, apartment unit, or place to live.

So in this sentence, 新しい部屋 probably means:

• a new apartment
• a new place
• a new rental unit

This is very common in housing contexts.

Because 部屋 is the direct object of 決める.

決める means to decide, to choose, or to settle on something.
The thing being chosen is often marked with を.

So:

• 部屋を決める = to choose/decide on a room

That is why the sentence has 新しい部屋を決めたいです.

Usually, no—not in this exact form.

With 決める, both patterns can appear, but they are used differently:

• Aを決める = decide/choose A
• Aに決める = decide on A

However, Aに決める is most natural when A is a specific option:

• この部屋に決めます = I’ll choose this room.
• 第一案に決めました = I decided on the first plan.

In your sentence, 新しい部屋 is still a general target, not one specific option, so を is the more natural choice.

It is the たい-form of the verb 決める.

• dictionary form: 決める = to decide
• stem: 決め
• たい added: 決めたい = want to decide
• polite ending: 決めたいです

So 決めたいです means I want to decide.

Because たい behaves grammatically like an い-adjective.

That means:

• plain form: 決めたい
• polite form: 決めたいです

This is similar to:

• うれしい → うれしいです
• 忙しい → 忙しいです

So 決めたいです is the normal polite way to say want to decide.

Mostly, yes.

The たい form is most naturally used for:

• your own desires
• asking about the listener’s desires in some contexts

Examples:

• 新しい部屋を決めたいです。 = I want to choose a new place.
• どの部屋に決めたいですか。 = Which room do you want to choose?

For a third person, Japanese often avoids directly stating their inner desire with たい unless it is clear from context or quotation. Instead, you often see:

• 決めたがっている = seems to want to decide
• 決めたいと言っている = says they want to decide

The sentence is ordered like this:

• 今月のうちに = time phrase
• 新しい部屋を = object
• 決めたいです = verb phrase

So literally it is something like:

• Within this month, a new room, want to decide

A more natural English order would be:

• I want to decide on a new room by the end of this month.

Japanese often puts time expressions early and the main verb at the end.

Yes, it is natural.

It sounds like something a person might say when talking about moving or apartment hunting.

Very natural alternatives include:

• 今月のうちに新しい部屋を決めたいです。
• 今月中に新しい部屋を決めたいです。

Both are good. The second one may sound a little more straightforward in everyday conversation.

They are only there to help learners read the sentence.

Normal Japanese is usually written without spaces:

今月のうちに新しい部屋を決めたいです。

So the spaced version is a study aid, not standard writing.