atarasii heya wo kimeru mae ni, mou itido naikensasete moraimasita.

Because 前に normally follows the dictionary form of a verb when you mean before doing that action.

• 決める前に = before deciding
• 食べる前に = before eating
• 寝る前に = before sleeping

The idea is that, at that point in the sentence, the decision has not happened yet.

A useful contrast is:

• 決める前に = before deciding
• 決めた後で = after deciding

So 決める前に is the normal grammar here.

In everyday Japanese, 部屋 literally means room, but in housing contexts it often means apartment unit, place, or the room/apartment you may rent.

So 新しい部屋 here most likely means:

• the new apartment
• the new place
• the room the speaker is thinking of moving into

It does not necessarily mean the room is newly built. It usually means new to the speaker.

内見 is a real-estate term. It means going to see the inside of a property before renting or buying it.

So it is more specific than just 見る.

• 見る = to look / see
• 内見する = to do a property viewing / inspect a place in person

You will often hear this when talking about apartments or houses.

It breaks down like this:

• 内見する = to view a property
• 内見させて = causative te-form, to let someone view
• もらいました = received that favor / permission

Together, V-させてもらう often means:

• to be allowed to do V
• to get to do V
• to have someone let you do V

So 内見させてもらいました means something like:

• I was allowed to do another viewing
• They let me view it again
• I got to see it again

It often carries a nuance of appreciation or acknowledgment that someone cooperated.

No. Here, the speaker is the one who did the viewing.

This is an important point:

• させる by itself can mean make/let someone do
• させてもらう means receive permission to do something yourself

So here the meaning is I was allowed to view it, not I made someone else view it.

Because the speaker is not only stating the action, but also showing that the action happened with someone’s permission or help.

Compare:

• 内見しました = I viewed it
• 内見させてもらいました = I was allowed to view it / they let me view it

In a real-estate situation, a second viewing usually has to be arranged by an agent, owner, or manager, so させてもらいました sounds very natural. It suggests:

• someone accommodated the request
• the speaker appreciates that
• it was not just a casual action done independently

Because 内見 here is being used as part of the verb 内見する.

So the structure is not:

• noun + object particle + another verb

It is:

• 内見する
• 内見させて
• 内見させてもらいました

In other words, 内見 is functioning as a verbal noun.

Japanese has many words like this:

• 勉強する
• 運転する
• 確認する
• 内見する

When they combine directly with する and forms built from する, you usually do not add を.

もう一度 means one more time or again.

So it tells you that the speaker had already done a viewing before, and this was a second viewing.

It modifies the later verb phrase:

• もう一度 内見させてもらいました
• I was allowed to view it one more time

Its position is very natural here.

Because in Japanese, subordinate parts of the sentence usually stay in plain form, even when the whole sentence is polite.

So this is normal:

• 決める前に、内見させてもらいました。

Not natural:

• 決めます前に

A good rule is:

• the final verb often carries the politeness
• earlier clauses often use plain forms

Because 決める is a transitive verb: you decide or choose something.

So:

• 部屋を決める = to decide on a room / choose a place

In English, we often say decide on a room, but Japanese just marks the thing being decided with を.

Neither is explicitly stated, because Japanese often leaves out information that is obvious from context.

Most likely:

• the subject is I
• the person who allowed it is an agent, landlord, owner, or management company

So the full idea is something like:

• Before deciding on the new place, I was allowed to view it once more.

But Japanese often does not need to spell out all of those roles.

Not necessarily.

決める often means to decide on, to settle on, or to choose. In this context, it usually means before making the final choice about the apartment.

It does not automatically mean the legal paperwork was already done. It is more about the speaker’s decision point.

No. Standard Japanese normally does not put spaces between words like this.

So it would usually be written as:

新しい部屋を決める前に、もう一度内見させてもらいました。

The spaces are just a learning aid to make the sentence easier to read.