На примерке портной предложил укоротить пальто.

Russian often uses на with events and scheduled activities:

• на уроке = at/in class
• на встрече = at a meeting
• на концерте = at a concert

A fitting is treated the same way, so на примерке is natural. If you want to talk about the fitting room, that would be в примерочной.

It is the prepositional singular form of примерка.

The pattern is:

• примерка → dictionary form
• на примерке → after на in this kind of at/during an event meaning

Портной is the subject of the sentence, in the nominative singular. It means tailor.

It looks a bit like an adjective because of its ending, but here it is a noun. The verb предложил is masculine singular past tense, which matches портной.

It can be understood as either, depending on context.

With an infinitive, предложить often means to suggest/propose doing something. But in a service situation, English often translates it as offered to shorten the coat, because a tailor is the person who would normally do that work.

So the Russian is a little broader than one single English wording.

After предложить, Russian very often uses an infinitive to say what action was proposed:

• предложил укоротить пальто = suggested/offered to shorten the coat

This is a very common and compact structure in Russian.

Because укоротить is perfective. It focuses on a completed result: the coat ends up shorter.

That is the natural choice here, because the tailor is proposing one concrete alteration. Укорачивать is imperfective and would sound more like an ongoing process, repeated action, or a general activity.

It helps form the verb meaning to make shorter / shorten.

In clothing-alteration contexts, укоротить is the normal verb:

• укоротить брюки = shorten the trousers
• укоротить юбку = shorten the skirt
• укоротить пальто = shorten the coat

Because пальто is an indeclinable noun in modern Russian. Its form stays the same in different cases.

In this sentence it is the direct object, so functionally it is in the accusative, but the word still looks exactly the same: пальто.

It is treated as neuter.

You can see that from adjective agreement:

• новое пальто
• длинное пальто

So even though пальто itself does not change, other words around it show its gender.

Russian often leaves that unstated when the context makes it obvious. At a fitting, everyone already knows whose coat is being discussed.

If you really want to make it explicit, моё пальто is the clearest way:

• На примерке портной предложил укоротить моё пальто.

Adding мне can make the structure less clear, because it may sound like the suggestion was addressed to me.

Yes. Russian word order is flexible.

The original sentence starts with На примерке to set the scene first:

• На примерке портной предложил укоротить пальто.

You could also say:

• Портной на примерке предложил укоротить пальто.

That is also possible, but the emphasis shifts slightly. The original version sounds very natural because it begins with the situation.

A useful stress-marked version is:

На приме́рке портно́й предложи́л укороти́ть пальто́.