Mam nadmiar ubrań.

Mam means I have. It is the 1st person singular present tense form of the verb mieć.

So the pattern is:

• mam = I have
• masz = you have
• ma = he/she/it has

In this sentence, Mam nadmiar ubrań literally starts with I have...

Because nadmiar requires the following noun to be in the genitive case.

The basic noun is:

• ubranie = a piece of clothing / a garment

Its plural is:

• ubrania = clothes

But after nadmiar, you do not use the normal nominative plural ubrania. You use the genitive plural:

• ubrań

So:

• nadmiar ubrań = an excess of clothes

This is one of the most important things to notice in the sentence.

Ubrań is genitive plural.

Here is the mini-pattern:

• singular nominative: ubranie
• plural nominative: ubrania
• plural genitive: ubrań

After nouns like nadmiar meaning excess, Polish commonly uses the genitive.

Nadmiar means an excess, too much, or more than needed.

So mam nadmiar ubrań means something like:

• I have an excess of clothes
• I have too many clothes
• I have more clothes than I need

Compared with za dużo, nadmiar can sound a bit more formal or abstract.

Yes, it is grammatical and understandable, but in everyday conversation many speakers would more naturally say:

• Mam za dużo ubrań = I have too many clothes

Mam nadmiar ubrań is fine, but it can sound a little more formal, written, or emphatic.

So:

• Mam nadmiar ubrań = correct, slightly more formal/bookish
• Mam za dużo ubrań = very common in speech

Because Polish does not use articles like English a, an, and the.

So Polish simply says:

• Mam nadmiar ubrań

and English has to decide from context whether to say:

• I have an excess of clothes
• I have too many clothes

This is completely normal in Polish.

Yes, ubrania is a normal, standard word for clothes.

A few related words:

• ubranie = one item of clothing / one garment
• ubrania = clothes
• ciuchy = clothes, but more informal, like clothes/stuff to wear

So ubrania is a safe, neutral choice.

Yes. In Polish, ubrania is a plural noun meaning clothes.

English often uses:

• clothes = plural
• clothing = uncountable

Polish usually uses ubrania in this kind of sentence, and then the genitive plural form becomes ubrań.

So even if English says clothing, Polish may still use a plural-based form.

The basic word order is:

• Mam = I have
• nadmiar = an excess
• ubrań = of clothes

So literally:

• I have excess of clothes

In natural English, that becomes:

• I have too many clothes

Polish word order is fairly flexible, but Mam nadmiar ubrań is a normal neutral order.

A rough pronunciation guide is:

• mam ≈ mahm
• nadmiar ≈ NAHD-myar
• ubrań ≈ OO-brań

A few useful notes:

• mi in nadmiar sounds roughly like mya
• ń is a soft n sound, similar to the ny sound in some pronunciations of canyon
• the stress is normally on the second-to-last syllable:
  • NAD-miar
  • U-brań

So the whole sentence is approximately:

• mahm NAHD-myar OO-brań

Yes, you could. It means almost the same thing:

• Mam za wiele ubrań = I have too many clothes

But in everyday speech, za dużo is usually more common than za wiele.

So in terms of naturalness:

1. Mam za dużo ubrań — most common everyday version
2. Mam za wiele ubrań — correct, a bit less common
3. Mam nadmiar ubrań — correct, somewhat more formal or stylistic

Yes, that is a very good idea.

A useful way to remember it is:

• nadmiar + genitive = excess of something

Examples:

• nadmiar pracy = an excess of work
• nadmiar obowiązków = too many duties
• nadmiar ubrań = too many clothes

If you learn the whole pattern, it will be much easier than trying to memorize each sentence separately.