この
この means “this” and points to the specific shared bathroom being discussed in 「この共用トイレ」. It is placed before a noun to identify something near or relevant to the speaker.
共用
共用 means “shared” or “communal” in 「この共用トイレ」. It describes a facility used by multiple people and can be placed before a noun to identify something shared.
トイレ
トイレ means “toilet” or “bathroom” in this dialogue. It names the shared facility and is the object in 「トイレを使って」.
を
を marks 「トイレ」 as the thing being used in 「トイレを使って」. It commonly comes after the object and before the action verb.
使って
使って means “use” in the permission pattern 「使ってもいいですか」. This form is used before 「もいいですか」 when asking whether using something is allowed.
も
In 「使ってもいいですか」, も contributes the sense “even if” to the permission pattern, so the question asks whether it is okay to use the bathroom. Here it does not mean “also.”
いい
いい means “okay” or “acceptable” in 「使ってもいいですか」. Together with 「も」 and 「ですか」, it asks whether an action is permitted.
です
です makes 「いいですか」 polite in this permission question. It gives the sentence a polite tone when speaking to another person.
か
か turns 「使ってもいいです」 into a question in 「使ってもいいですか」. It is placed at the end of this polite question.
洗面台
洗面台 means “sink” or “washbasin” in this shared bathroom. In 「洗面台の周り」, it is the place whose surrounding area should be kept clean.
の
の connects 「洗面台」 with 「周り」 in 「洗面台の周り」, showing that the area is around the sink. The pattern 「Xの周り」 identifies the area surrounding X.
周り
周り means “the area around” something in 「洗面台の周り」. It is useful for describing the surrounding area of a place or object.
きれい
きれい means “clean” in 「きれいにしてください」. It describes the clean state requested for the area around the sink.
に
に marks the state in 「きれいにして」, showing that the sink area should be made or kept clean. It connects the state 「きれい」 to the action of making it so.
して
して means “make or keep it” in the request 「きれいにしてください」, with the understood object being the sink area. It is the action form that comes before 「ください」 in this polite request.
ください
ください means “please do” in 「きれいにしてください」. It turns the preceding action into a polite request, such as asking someone to keep an area clean.
ペーパータオル
ペーパータオル means “paper towel” in 「ペーパータオルが必要です」. It is the item the speaker needs and can be used as the item before 「が必要です」.
が
が marks 「ペーパータオル」 as the item that is needed in 「ペーパータオルが必要です」. The pattern 「Xが必要です」 states that X is needed.
必要
必要 means “needed” or “necessary” in 「ペーパータオルが必要です」. With 「が」, it describes an item required by the speaker.
近く
近く means “nearby” or “the vicinity” in 「洗面台の近くに」. The pattern 「Xの近く」 describes a place near X.
何枚
何枚 refers to an unspecified number of sheets in 「何枚かあります」. 枚 is used here for flat items such as paper towels, and the full expression means that some sheets are available.
あります
あります means “there are” or “are available” in 「何枚かあります」. With a location marked by 「に」, it tells where the items can be found.
これ
これ means “this thing” and refers to the item the speaker is holding or indicating in 「これはゴミ箱に入れますか」. It is used when the relevant item is close to the speaker.
は
は marks 「これ」 as the topic in 「これはゴミ箱に入れますか」, giving the sense “as for this.” It is useful for making the item being discussed the topic of a question.
ゴミ箱
ゴミ箱 means “trash bin” in 「ゴミ箱に入れますか」. With 「に」, it identifies the container where the item may be put.
入れます
入れます means “put in” in the question 「ゴミ箱に入れますか」. The pattern 「Xに入れます」 describes putting something into X.
小さい
小さい means “small” in 「小さいゴミ箱」. It comes before the noun and specifies which trash bin is meant.
入れて
入れて means “put it in” or “place it inside” in 「小さいゴミ箱に入れてください」. It is used before 「ください」 to make a polite request to put something into a container.
私
私 means “I” or “me” in 「私も洗面台をすぐに拭きます」. Together with 「も」, 「私も」 means that the speaker will do this as well.
すぐ
すぐ means “right away” or “quickly” in 「すぐに拭きます」. It gives the timing of the wiping action and commonly comes before the verb.
拭きます
拭きます means “wipe” in 「洗面台をすぐに拭きます」. The pattern 「Xを拭きます」 describes wiping X, such as a sink or another surface.
それ
それ means “that” in 「それは次の人の役に立ちます」 and refers back to the wiping action just mentioned. It can be used to refer back to something another person has said or done.
次
次 means “next” in 「次の人」. With 「の」 before a noun, it identifies the person who comes or uses the space afterward.
人
人 means “person” in 「次の人」. The expression refers to the next person who will use the shared bathroom.
役に立ちます
役に立ちます as a whole means “be helpful” or “be useful” in 「次の人の役に立ちます」. 役 refers to a helpful role or benefit, に links that usefulness to the person helped, and 立ちます completes this expression with the meaning “be of service” here. The pattern 「Xの役に立ちます」 says that something is helpful to X.