Konewka stoi za domem obok grabi.

Because after za in a location meaning, Polish uses the instrumental case.

Here, za domem means behind the house as a fixed location, so dom changes to domem.

A very useful contrast is:

• za domem = behind the house / located behind the house
• za dom = to behind the house / movement to that place

With an inanimate masculine noun like dom, the accusative form looks the same as the basic dictionary form, so:

• Konewka stoi za domem. = The watering can is behind the house.
• Idę za dom. = I’m going behind the house.

So the form domem tells you this is about position, not movement.

Because obok requires the genitive case, and grabi is the genitive form of grabie.

The noun grabie is a special kind of noun called plural-only (pluralia tantum). Even when it refers to one rake as an object, grammatically it behaves like a plural noun.

So:

• basic form: grabie
• after obok: grabi

Compare:

• Widzę grabie. = I see the rake / rake(s).
• Konewka stoi obok grabi. = The watering can is next to the rake / rake(s).

So grabi is not random—it is there because obok needs the genitive.

In practice, it can refer to a rake as a tool, even though grammatically the noun is plural.

That can feel strange to English speakers, because English distinguishes clearly between rake and rakes. In Polish, grabie is usually treated as a plural-form noun for the tool itself.

So in a sentence like this, obok grabi will often be understood as:

• next to the rake

But depending on context, it could also mean:

• next to the rakes

Context usually makes it clear.

Because Polish very often uses position verbs where English just says is.

Stać means to stand, and it is commonly used for objects that are in an upright position. A watering can can naturally be described as standing somewhere.

So:

• Konewka stoi za domem. literally = The watering can is standing behind the house
• natural English = The watering can is behind the house

Polish often distinguishes:

• stoi = stands
• leży = lies
• wisi = hangs

Examples:

• Butelka stoi na stole. = The bottle is on the table.
• Książka leży na stole. = The book is on the table.
• Lampa wisi nad stołem. = The lamp is over the table.

So stoi sounds natural and specific.

No. Za can take different cases depending on meaning.

In this sentence, za means behind in a static location sense, so it takes the instrumental:

• za domem = behind the house

But when za expresses movement to a place, it usually takes the accusative:

• Idę za dom. = I’m going behind the house.

So a good rule is:

• location → often instrumental
• movement/destination → often accusative

This location-vs-movement contrast is very common with Polish prepositions.

Obok takes the genitive case.

That is why you get:

• obok domu = next to the house
• obok grabi = next to the rake / rakes

So in this sentence:

• za domem → instrumental after za
• obok grabi → genitive after obok

This means the sentence contains two different prepositions, each controlling a different case.

Because Polish does not have articles like English a/an and the.

So:

• konewka can mean a watering can or the watering can
• domem can mean a house or the house
• grabi can mean a rake, the rake, or sometimes rakes, depending on context

Polish relies on context rather than articles to show whether something is definite or indefinite.

That is why the same sentence could be translated in slightly different ways depending on context:

• A watering can is standing behind a house next to a rake.
• The watering can is behind the house next to the rake.

Polish word order is fairly flexible.

The sentence Konewka stoi za domem obok grabi is a normal, neutral way to say it, but other orders are possible, for example:

• Za domem obok grabi stoi konewka.
• Obok grabi, za domem, stoi konewka.

These versions still mean basically the same thing, but they change the focus or what sounds emphasized.

Very roughly:

• Konewka stoi... puts the watering can first as the topic
• Za domem... stoi konewka emphasizes the location a bit more

So yes, the order can change, but the original sentence is a natural default.

In theory, the phrase structure can feel a little ambiguous, because English speakers may wonder whether it means:

• the watering can is behind the house and next to the rake, or
• the house is next to the rake

In normal usage, the intended reading is usually:

• The watering can is behind the house, next to the rake.

That is, obok grabi is understood as part of the watering can’s location.

If you wanted to make that extra clear, you could rearrange the sentence:

• Konewka stoi obok grabi, za domem.
• Za domem, obok grabi, stoi konewka.

So the original is understandable, but context and word order can help remove any slight ambiguity.