"I have got a black cat."

Translation: Ja mam czarnego kota.

[Arnoldpitt]

why czarn "ego"

[Vengir]

Adjective also declinate. „Czarnego” is „czarny” in accusative case.

[5134ad]

when is the suffix ego used? and when is the suffix ch used?

[immery]

I don't think we have -ch suffix, there is always some vovel before,

I assume you are asking about difference between czarn-ego and czarn-ych

-ego is genitive adjectives describing masculine and neuter nouns, and accusative adjectives for masculine nouns that have genitive=accusative, or their own accsative form

-ych/ich is plural - all genitive, all locative and masculine personal accusative.

so

Mam czarnego kota (accusative) (I have a black cat)
Nie mam czarnego kota (genitive) (I don't have a black cat)

Mam czarny ołówek (accusative)(I have a black pencil)
Nie mam czarnego ołówka (genitive) (I don't have a black pencil)

Mam czarne koty (accusative) (I have black cats)
Nie mam czarnych kotów (genitive) (I don't have black cats)
Mówię o czarnych kotach (locative) (I talk about black cats)

Mam czarnych kolegów (I have black friends)
Nie mam czarnych kolegów (genitive) (I don't have black friends)
Mówię o czarnych kolegach (locative) (I talk about black friends)

[Gary726273]

Doesn't "I have got a black cat" imply that you have just caught it or obtained it in polish? Rather than "I have a black cat" . Should the word "got" be translated?

[Jellei]

What is meant is just "I have a black cat". Which will be the default English sentence now.