Когда в метро тесно, мне хочется расстегнуть воротник и подышать глубже.

In Russian, the present-tense verb to be is usually omitted. So в метро тесно means it is cramped/crowded in the metro, even though there is no written word for is.

Also, тесно here is not an adjective agreeing with a noun. It is a predicative word describing a situation or state: it’s cramped, there isn’t enough room.

It can be understood as either, depending on context. In this sentence it has a general, repeated-situation meaning, so in natural English it is often closest to when/whenever:

• When the metro is crowded...
• Whenever it’s cramped in the metro...

Russian когда often covers both ideas.

Мне хочется is a very common way to say I feel like... or I have the urge to... It sounds softer, more spontaneous, and more about an inner feeling.

Compare:

• Я хочу расстегнуть воротник = I want to unbutton my collar
  More direct and deliberate.
• Мне хочется расстегнуть воротник = I feel like unbuttoning my collar
  More like an urge or impulse caused by the situation.

So in this sentence, мне хочется fits the idea of reacting to discomfort.

Because хочется is part of an impersonal construction. In Russian, many feelings, sensations, and involuntary states are expressed with:

• a dative experiencer +
• an impersonal verb or state word

So мне хочется is literally something like to me, it is wanted or to me, there is a desire.

This pattern is very common:

• мне холодно = I’m cold
• мне грустно = I’m sad
• мне хочется спать = I feel like sleeping / I’m sleepy

The dictionary form is хотеться. It is related to хотеть but used impersonally.

• хотеть = to want
• хотеться = to feel like, to want involuntarily

In this sentence, хочется is the present-tense form used with мне.

After хочется, Russian usually uses an infinitive to say what someone feels like doing.

So:

• мне хочется расстегнуть воротник
• мне хочется подышать глубже

Both infinitives depend on хочется. The sentence structure is basically:

When it’s cramped in the metro, I feel like [doing X] and [doing Y].

They describe actions seen as single, bounded, or goal-oriented responses to the situation.

• расстегнуть is perfective: to unbutton / undo
  • a one-time completed action
• подышать is also perfective, but with a special nuance:
  • to breathe for a while
  • to take some breaths
  • to get a bit of air

If you used imperfective forms, the focus would shift more toward the process in general rather than the immediate urge to do those actions.

Подышать often means to breathe a bit, to take some breaths, or to breathe for a short time. It is very natural in situations like wanting relief.

So here, подышать глубже suggests something like:

• take a few deeper breaths
• breathe more deeply for a bit

If you said дышать глубже, that would sound more general, like the process itself rather than a short relieving action.

Глубже is the comparative form: deeper / more deeply.

So подышать глубже means to breathe more deeply or to take deeper breaths.

This makes sense because the sentence suggests contrast with the current uncomfortable situation: when it’s crowded, you want to breathe more deeply than you can now.

Compare:

• дышать глубоко = to breathe deeply
• дышать глубже = to breathe deeper / more deeply

Both are possible in Russian, but глубже fits the idea of adjustment or comparison especially well.

Воротник is in the accusative case because it is the direct object of расстегнуть.

However, for masculine inanimate nouns, the accusative singular looks the same as the nominative singular. So:

• nominative: воротник
• accusative: воротник

That is why the form does not visibly change.

Russian often leaves out possessive words like my, your, or his when the owner is obvious from context, especially with:

• clothing
• body parts
• personal belongings in immediate use

So расстегнуть воротник naturally means unbutton my collar here, because it is clearly the speaker’s own collar.

You could say расстегнуть свой воротник, but it would usually sound unnecessary unless you wanted to stress possession or avoid ambiguity.

Метро is an indeclinable noun, which means its form does not change across cases.

So you get:

• метро
• в метро
• из метро
• к метро

The case is still determined by the preposition and function, but the word itself stays the same in form.

Because Когда в метро тесно is a subordinate clause, and Russian separates subordinate clauses from the main clause with a comma.

So the structure is:

• Когда в метро тесно, = subordinate clause
• мне хочется расстегнуть воротник и подышать глубже. = main clause

This is standard Russian punctuation.