Learn Italian: Ci sono nove persone là. - There are nine people there.

In Italian, cardinal numbers from two upwards do not change their endings to match the gender of the noun. The number nove stays exactly the same whether you are counting masculine nouns or feminine nouns like persone. Only the number one (uno or una) changes for gender.

Why do we use ci sono here instead of c'è?

Ci sono means "there are" and is used because we are talking about a plural amount, which is nove persone. If there were only one person, you would use the singular c'è meaning "there is", for example: c'è una persona là.

The word persone is feminine. Does that mean the group only includes women?

Not at all! The singular word persona and its plural persone are always grammatically feminine, regardless of the actual gender of the people you are talking about. A group of nine men is still called nove persone.

Why does the word là have an accent mark on the letter a?

The accent mark completely changes the meaning of the word. With the accent, là means "there". Without the accent, la is the feminine word for "the" or "her". Written accents are very common in Italian to tell apart short words that are otherwise spelled the same way.