haha to soudansite kara, sono heya wo keiyakusimasu.

Here, と means with.

• 母と相談する = to discuss/consult with one’s mother

This use of と shows the other person involved in the discussion.

A useful comparison:

• 母と話す = talk with my mother
• 母と相談する = discuss/consult with my mother

With 相談する, you may also see に:

• 母に相談する = consult my mother / ask my mother for advice

The nuance is slightly different:

• と相談する focuses more on discussing something together
• に相談する focuses more on going to someone for advice

In this sentence, と sounds very natural.

相談してから means after discussing/consulting.

It is made from:

• 相談する = to discuss / to consult
• 相談して = te-form
• 〜てから = after doing ~

So:

• 母と相談してから = after discussing it with my mother

This pattern is very common:

• 食べてから行きます = I’ll go after eating
• 考えてから決めます = I’ll decide after thinking

So the sentence shows the order clearly:

1. discuss it with mother
2. then sign the contract

Because 〜てから and 〜たから mean completely different things.

• 〜てから = after doing ~
• 〜たから = because ~ did

So:

• 相談してから、契約します = After discussing it, I will sign the contract.
• 相談したから、契約します = Because I discussed it, I will sign the contract.

In your sentence, the meaning is about sequence, not reason, so 〜てから is the correct form.

Japanese non-past forms often cover both present and future.

So 契約します can mean:

• I sign
• I will sign

In this sentence, because of 〜てから and the overall context, it naturally refers to a future action:

• After consulting with my mother, I’ll sign the contract for that room.

This is very normal in Japanese. You do not need a separate future tense form.

その means that, and it modifies 部屋:

• その部屋 = that room

This usually refers to a room that is already known in the conversation, such as a specific apartment room both speakers are talking about.

Quick comparison:

• この部屋 = this room (near the speaker)
• その部屋 = that room (near the listener, or already mentioned)
• あの部屋 = that room over there / that room not near either person

So その部屋 often feels like that room we’re talking about.

を marks the direct object of the verb.

Here:

• その部屋を = that room
• 契約します = make/sign a contract

So the room is the thing being contracted for.

In English, we usually say sign a contract for the room rather than contract the room, but Japanese often says it more directly:

• 部屋を契約する

In real estate contexts, this is natural Japanese. Depending on context, you might also hear:

• その部屋を借ります = I’ll rent that room
• その部屋に決めます = I’ll choose that room

But 契約します emphasizes the act of formally making the agreement.

Yes, in this sentence 母 naturally means my mother.

Japanese often omits my, your, his, etc. when the meaning is clear from context. So:

• 母 can mean my mother
• 父 can mean my father

Also, Japanese commonly uses the plain family terms when talking about one’s own family to other people:

• 母 = my mother
• 父 = my father

You could say 私の母, but it is often unnecessary unless you need emphasis or clarity.

Because Japanese very often omits the subject when it is obvious from context.

So even though the sentence does not say 私は, the listener understands that the speaker means something like:

• I will sign the contract for that room after consulting with my mother.

This is one of the biggest differences from English. Japanese sentences often leave out:

• the subject
• the object
• other details

as long as the meaning is clear.

No, it is not grammatically required, but it is very common and natural.

• 母と相談してからその部屋を契約します。
• 母と相談してから、その部屋を契約します。

Both are correct.

The comma simply makes the sentence easier to read by separating the after doing X part from the main action.

Both are possible, depending on context.

• discuss with my mother
• consult my mother
• talk it over with my mother

In this sentence, 相談する suggests talking about the decision before acting. Since the topic is renting or contracting a room, consult or talk it over with often sounds very natural in English.

Nuance:

• discuss = fairly neutral
• consult = slightly more like asking for advice
• talk it over = very natural conversational English

So all of these can fit the sentence well.