Я чувствую запах кофе на кухне.

Russian often expresses I smell... as я чувствую запах..., literally I feel/perceive the smell of....

• чувствовать means to feel / to sense / to perceive
• запах means smell / scent / odor

This is a very natural way to talk about noticing a smell.

A different verb, нюхать, means to sniff or to smell something on purpose. So:

• Я чувствую запах кофе = I can smell coffee
• Я нюхаю кофе = I am sniffing the coffee

You usually include запах to make it clear that you mean the smell of coffee, not coffee itself.

• Я чувствую запах кофе = I smell coffee / I can sense the smell of coffee
• Я чувствую кофе is much less natural in this meaning and could sound unclear or context-dependent

So запах helps specify exactly what is being perceived.

запах is in the accusative singular because it is the direct object of чувствую.

The verb чувствовать takes a direct object:

• чувствую что? → запах

Because запах is a masculine inanimate noun, its accusative form is the same as its nominative form:

• nominative: запах
• accusative: запах

So the form does not visibly change.

кофе depends on запах and answers the idea smell of what?

In Russian, nouns like запах are commonly followed by the genitive:

• запах кофе = smell of coffee
• запах хлеба = smell of bread
• запах дыма = smell of smoke

So here кофе is functioning as genitive, even though its form does not change.

Because кофе is an indeclinable noun in standard Russian. That means its form stays the same in different cases:

• nominative: кофе
• genitive: кофе
• accusative: кофе
• etc.

So even though it is grammatically the genitive here after запах, it still looks exactly the same.

Also, кофе is traditionally treated as masculine in standard Russian, even though it ends in -е.

This is an idiomatic feature of Russian. With кухня, Russian usually says на кухне for in the kitchen / in the kitchen area.

So:

• на кухне = in the kitchen
• в кухне is much less common and usually sounds unnatural in ordinary speech

This is just one of those preposition choices that has to be learned as a pattern. Russian often uses на with certain places where English uses in.

кухне is in the prepositional case because it follows на in a location meaning.

• на кухне = in the kitchen / on the kitchen premises

When на means location, it commonly takes the prepositional case.

Compare:

• на кухне = in the kitchen (location)
• на кухню = to the kitchen (motion toward)

So if there were movement, Russian would use the accusative instead.

In practice, it can be understood from context, and often the distinction is not very important.

Я чувствую запах кофе на кухне most naturally means something like:

• I smell coffee in the kitchen
• There is a smell of coffee in the kitchen, and I notice it

Depending on context, на кухне may refer to:

• the place where the speaker is sensing the smell
• the place where the smell is located
• both at once

Russian leaves this kind of attachment to context quite often.

No. Russian often omits subject pronouns when the verb form already makes the subject clear.

• Чувствую запах кофе на кухне = I smell coffee in the kitchen
• Я чувствую запах кофе на кухне = same basic meaning, but я can add emphasis, contrast, or simply sound more explicit

Because чувствую clearly marks I, the pronoun is optional in many contexts.

Yes. Russian word order is flexible, and changing it usually changes emphasis, not the core meaning.

For example:

• Я чувствую запах кофе на кухне = neutral
• На кухне я чувствую запах кофе = emphasizes the location
• Запах кофе я чувствую на кухне = emphasizes the smell of coffee

So the sentence structure can move around depending on what the speaker wants to highlight.

Yes. A very common alternative is:

• На кухне пахнет кофе.

This literally means It smells like coffee in the kitchen or The kitchen smells of coffee.

The difference is roughly:

• Я чувствую запах кофе на кухне = focuses on my perception
• На кухне пахнет кофе = focuses on the smell in the place itself

Both are natural, but they are framed a little differently.