Learn Polish: U babci jest mały piesek i piękny kwiatek. - At grandmother's place there is a small doggy and a beautiful little flower.

Both of these come from masculine nouns: pies (dog) and kwiat (flower). To make a masculine noun smaller or cuter, we usually add the suffix -ek. So, pies becomes piesek (doggy), and kwiat becomes kwiatek (little flower).

Since piesek already means a little dog, isn't it redundant to add the word mały (small)?

It might seem redundant in English, but in Polish, it is very common and sounds perfectly natural! Adding adjectives like mały to a diminutive emphasizes how small or cute the thing is, or it simply expresses affection.

Why does the sentence start with U babci instead of U babcia?

The preposition u, meaning at someone's place, always requires the following noun to be in the Genitive case. The base word is babcia (grandmother), and its Genitive form is babci.

Where is the word for there in the Polish translation of there is?

Polish doesn't use a filler word like there in these phrases. To say there is or there are, you simply use the verb być (to be) on its own. Here, jest handles the whole meaning of there is.