После ремонта нужно убрать инструменты.

Because после requires the genitive case.
The base form is ремонт, but after после it becomes ремонта.

Compare:

• после работы = after work
• после урока = after the lesson
• после ремонта = after the repair / after the renovation work

So this is a case-governed form, not a different word.

It means after the repair work or after the renovation. In this sentence, ремонт usually refers to repair or renovation activity, especially in a home, room, or building.

So после ремонта means after that work is finished, not just after fixing one tiny thing.

Russian often leaves the subject unstated when it is general or unimportant.
In нужно убрать инструменты, the meaning is something like:

• it is necessary to put away the tools
• the tools need to be put away
• someone needs to put away the tools
• we need to put away the tools

The sentence is impersonal. It focuses on the necessity of the action, not on who does it.

Нужно is an impersonal predicative word meaning it is necessary, need to, or must in a general sense.

It is commonly followed by an infinitive:

• нужно идти = it is necessary to go
• нужно работать = one needs to work
• нужно убрать инструменты = the tools need to be put away

English often uses a dummy subject it in this kind of sentence, but Russian does not need one here.

Убрать is the perfective infinitive, while убирать is imperfective.

Here, the sentence is about completing one concrete action: put the tools away / clear them away. That is why убрать is natural.

• нужно убрать инструменты = the task is to finish putting the tools away
• нужно убирать инструменты could suggest a repeated, habitual, or process-oriented idea, depending on context

With нужно + infinitive, Russian often uses the perfective when the speaker means a single necessary completed action.

Here убрать means something like:

• put away
• clear away
• tidy away
• remove from where they are lying around

It does not necessarily mean clean in the sense of washing or scrubbing. It means making the tools no longer be out in the work area.

The dictionary form is инструменты because it is plural nominative.
In this sentence it is plural accusative because it is the direct object of убрать.

For inanimate plural nouns, nominative and accusative are usually the same. So:

• nominative: инструменты
• accusative: инструменты

That is why the form does not change here.

Yes. That is a very natural translation.

Because the Russian sentence is impersonal, English can translate it in several ways:

• After the repairs, the tools need to be put away.
• After the repair work, we need to put the tools away.
• After the renovation, it’s necessary to put away the tools.

The exact English wording depends on style, but the Russian meaning stays the same.

Yes, in most everyday situations:

• После ремонта нужно убрать инструменты.
• После ремонта надо убрать инструменты.

Both mean basically the same thing.

Very roughly:

• надо is often a bit more conversational
• нужно can sound slightly more neutral or formal

But in this sentence, either one works well.

No, Russian word order is flexible.
После ремонта нужно убрать инструменты is a normal, neutral order.

You could also say:

• Инструменты нужно убрать после ремонта.
• Нужно убрать инструменты после ремонта.

These versions are still grammatical, but the focus shifts slightly:

• putting после ремонта first sets the time frame first
• putting инструменты earlier can emphasize the tools
• putting нужно убрать first can emphasize the required action

So the original version is natural and neutral, not the only possible order.

Russian has no articles.
So инструменты can mean:

• the tools
• tools
• sometimes even some tools

The exact meaning comes from context. In this sentence, English will usually use the tools, because the tools are understood from the repair situation.

It can mean either, depending on context. In everyday Russian, ремонт is often broader than English repair and can include renovation work in a room, apartment, or house.

So in this sentence, после ремонта might mean:

• after the repair job
• after the renovation work
• after doing work on the place

If the context is a home or room, after the renovation may sound especially natural in English.