mensetu no mae ha, sinkokyuu wo suru you ni site imasu.

Both can exist, but 面接の前 is the more straightforward and standard way to say before the interview.

• 面接 = interview
• 前 = before / in front of
• Noun + の + 前 = before noun

So:

• 面接の前 = before the interview

You may also see compact compounds like 出発前 or 食事前, but for learners, Nの前 is the safest and most general pattern.

は marks 面接の前 as the topic: as for before an interview...

So the sentence has a nuance like:

• Before interviews, I make sure to take deep breaths.

It can also suggest a mild contrast, depending on context, such as:

• Before interviews, I do deep breathing
  (maybe implying that at other times I do something else, or not necessarily this)

This は does not have to be translated directly into English.

面接の前に would also be natural in many contexts. The difference is mainly nuance.

• 面接の前に focuses more directly on the time when the action happens: before the interview
• 面接の前は makes before the interview the topic: when it comes to before interviews...

Also, time expressions in Japanese often do not need に, especially with words like 前, 後, 今日, 明日, etc.

So this sentence is natural as written, and 面接の前に、深呼吸をするようにしています would also be possible, with a slightly different feel.

深呼吸 is a noun meaning deep breathing or a deep breath. To turn it into an action, Japanese commonly adds する.

• 深呼吸 = deep breath / deep breathing
• 深呼吸する or 深呼吸をする = to take a deep breath / to do deep breathing

This is a very common pattern in Japanese:

• 勉強する = study
• 運動する = exercise
• 練習する = practice

So 深呼吸をする literally means to do deep breathing.

Yes, you can say both:

• 深呼吸をする
• 深呼吸する

Both are correct.

The version with を makes it clearer that 深呼吸 is being treated as a noun plus する. In everyday Japanese, many noun + する combinations can appear either with or without を.

So:

• 深呼吸をする = slightly more explicit
• 深呼吸する = a bit more compact

In this sentence, 深呼吸をする sounds perfectly natural.

This is one of the most important parts of the sentence.

Verb dictionary form + ようにしている means:

• make a point of doing
• try to do regularly
• have a habit of doing
• make sure to do

So:

• 深呼吸をするようにしている = I make a point of taking deep breaths / I try to take deep breaths

It usually implies an intentional habit, not just a one-time action.

This is different from simply saying:

• 深呼吸をしています = I am taking deep breaths / I take deep breaths

The ようにしている adds the idea of conscious effort or routine.

Because ようにしている is the usual form for talking about an ongoing habit or practice.

• 〜ようにしている = I make it a habit to...
• 〜ようにしています = the polite version

Here, している does not mean the speaker is currently in the middle of breathing deeply right now. It means this is their regular practice.

So:

• 深呼吸をするようにしています = I try to take deep breaths / I make sure to take deep breaths

If you said 深呼吸をするようにします, it would sound more like:

• I will try to take deep breaths
• I’ll make it a habit to take deep breaths

That sounds more like a decision from now on, rather than an existing habit.

Yes, the subject is omitted, which is very normal in Japanese.

From context, the natural understanding is:

• I make a point of taking deep breaths before interviews.

Japanese often leaves out words like I, you, or he/she when they are obvious from context.

So even though 私 is not written, the sentence still sounds complete and natural.

It can be understood either way, depending on context.

In this sentence, 深呼吸をする probably means something like:

• take a deep breath
• do some deep breathing

The exact number is not important here. The idea is simply that the speaker intentionally calms themselves by breathing deeply before an interview.

So a natural English translation might be singular or plural, depending on style:

• I make sure to take a deep breath before interviews.
• I make sure to take deep breaths before interviews.

Both capture the idea.

Here are the main readings:

• 面接 → めんせつ
• 前 → まえ
• 深呼吸 → しんこきゅう
• する → する
• ようにしている → ようにしている

So the full sentence is read:

めんせつ の まえ は、しんこきゅう を する よう に して います。

It can lean toward a general habit, especially because of ようにしています.

So the overall feeling is:

• Before interviews, I make a point of taking deep breaths.

Even though 面接 does not have a plural marker, Japanese often uses the plain noun to talk about a category in general.

If the context were about one particular interview, it could also mean:

• Before the interview, I make sure to take deep breaths.

But without more context, the habitual reading is the strongest because of ようにしています.