Sortuję garderobę tylko wtedy, gdy mam nadmiar ubrań.

Sortuję is the 1st person singular present tense form of sortować, which means to sort, to organize, or to go through things and arrange them.

So sortuję means I sort or I am sorting, depending on context.

In this sentence, it is best understood as a habitual/general present: I sort my wardrobe only when I have too many clothes / an excess of clothes.

Also, sortować is an imperfective verb, which fits well because the sentence describes a repeated or general action, not one completed event.

Because garderobę is the accusative singular form of garderoba.

Here, garderoba is the direct object of the verb sortuję:

• sortować co? → garderobę

Since garderoba is a feminine noun, its accusative singular usually ends in -ę:

• nominative: garderoba
• accusative: garderobę

This is very common with feminine nouns in Polish.

Garderoba can mean a few related things, depending on context:

• wardrobe in the sense of your collection of clothes
• closet/dressing area
• sometimes even cloakroom

In this sentence, it most likely means wardrobe in the broad sense of your clothes / your clothing collection / the contents of your closet.

That is why the sentence sounds natural together with nadmiar ubrań — it is talking about having too many clothes and then sorting through your wardrobe.

Polish often leaves out possessive words like my, your, his, etc. when the meaning is obvious from context.

So:

• Sortuję garderobę can naturally mean I sort my wardrobe

You could say sortuję swoją garderobę, but it is not necessary here, and often it sounds less natural unless you want extra emphasis.

Also, Polish has no articles, so there is no direct equivalent of the wardrobe either.

Tylko wtedy, gdy means only when.

It is a very common pattern:

• wtedy, gdy = when / at the time when
• tylko wtedy, gdy = only when

So the sentence structure is:

• I sort my wardrobe only when...

You will also hear the shorter version:

• tylko gdy mam nadmiar ubrań

That is also correct. Adding wtedy makes the structure a bit more explicit and slightly more emphatic.

Both gdy and kiedy can mean when.

In many sentences, they are interchangeable:

• tylko wtedy, gdy...
• tylko wtedy, kiedy...

However:

• gdy can sound a bit more formal or written
• kiedy is often more conversational
• after wtedy, gdy is especially common and sounds very natural

So in this sentence, gdy is perfectly normal.

Because gdy introduces a subordinate clause, and in Polish such clauses are normally separated by a comma.

So:

• Sortuję garderobę tylko wtedy, gdy mam nadmiar ubrań.

The comma is required in standard Polish punctuation.

Nadmiar means an excess or too much of something. After nadmiar, Polish uses the genitive case.

That is why you get:

• nadmiar ubrań = an excess of clothes

Not:

• nadmiar ubrania

because that would be the wrong case here.

Also, mam dużo ubrań is absolutely possible, but it means I have a lot of clothes, while mam nadmiar ubrań sounds a bit more like I have more clothes than I need.

So:

• dużo ubrań = many/a lot of clothes
• nadmiar ubrań = an excess of clothes, too many clothes

Ubrań is the genitive plural of ubranie.

Basic forms:

• singular: ubranie = a piece of clothing / clothing item
• plural nominative: ubrania = clothes
• plural genitive: ubrań

It is genitive plural here because it depends on nadmiar:

• nadmiar czego? → ubrań

This is a very important Polish pattern: words expressing quantity, amount, absence, excess, etc. often require the genitive.

Because Polish present tense is often used for habits, general truths, and repeated actions.

So sortuję here does not mean only I am sorting right now. It can also mean:

• I sort
• I tend to sort
• I sort whenever this situation happens

That is exactly how English present simple works in many cases too.

Yes. Polish word order is fairly flexible, and changing it usually changes emphasis, not the basic meaning.

For example, these are all possible:

• Sortuję garderobę tylko wtedy, gdy mam nadmiar ubrań.
• Tylko wtedy sortuję garderobę, gdy mam nadmiar ubrań.
• Garderobę sortuję tylko wtedy, gdy mam nadmiar ubrań.

The original version is natural and neutral. Other versions may sound more emphatic or stylistically marked.

Yes. The sentence is correct, but some speakers might choose a more everyday phrasing, for example:

• Sortuję ubrania tylko wtedy, gdy mam ich za dużo.
• Robię porządki w garderobie tylko wtedy, gdy mam za dużo ubrań.

These sound a bit more conversational.

Your original sentence is still good Polish; it just sounds slightly more formal or deliberate because of garderobę and nadmiar ubrań.