Al pati de la meva tieta hi ha dos tests amb tomàquets i un amb flors.

Because a + el normally contracts to al in Catalan.

• a el pati → al pati
• This means in/to the patio/courtyard, depending on context

This is very similar to Spanish al. In this sentence, al pati means in the patio / in my aunt’s patio.

Pati usually means patio, courtyard, or sometimes a yard-like outdoor area attached to a house or building.

So Al pati de la meva tieta is referring to the outdoor patio/courtyard area belonging to the aunt.

Catalan usually expresses possession with de:

• el pati de la meva tieta = my aunt’s patio
• literally: the patio of my aunt

This is very common in Catalan. While English often prefers the ’s form, Catalan normally uses de + possessor.

In Catalan, possessives usually come after the definite article:

• la meva tieta = my aunt
• el meu germà = my brother
• els nostres amics = our friends

So unlike English, Catalan typically uses article + possessive + noun, not just possessive + noun.

Tia means aunt.

Tieta is the diminutive form, and it can sound:

• more affectionate
• more familiar
• sometimes simply more natural in family speech

So la meva tieta still means my aunt, but with a warmer or more familiar tone than la meva tia.

Hi ha means there is or there are.

Examples:

• Hi ha un llibre. = There is a book.
• Hi ha dos llibres. = There are two books.

In your sentence:

• hi ha dos tests... = there are two pots...

This is one of the most common Catalan expressions.

Because hi ha does not change for singular and plural in standard Catalan.

• Hi ha un test. = There is one pot.
• Hi ha dos tests. = There are two pots.

So unlike English there is / there are, Catalan keeps hi ha the same.

In modern Catalan, learners usually treat hi ha as a fixed expression meaning there is / there are.

Historically and grammatically, hi is a locative pronoun, related to the idea of there or in that place. But in practice, when you learn Catalan, it is best to memorize hi ha as a whole unit.

So:

• hi ha = there is / there are

Here test means a flowerpot or plant pot.

So:

• dos tests = two pots

Be careful: this is not the English word test. It is a Catalan noun with a completely different meaning.

Because many Catalan nouns form the plural by adding -s:

• test → tests
• tomàquet → tomàquets
• flor → flors

So dos tests simply means two pots.

Catalan often leaves out a noun when it is already understood.

So:

• dos tests amb tomàquets i un amb flors

means:

• two pots with tomatoes and one pot with flowers

The second test is omitted because it would be repetitive. English does the same:

• two pots with tomatoes and one with flowers

Because un is standing in for un test.

The full version would be:

• dos tests amb tomàquets i un test amb flors

But Catalan naturally omits the repeated noun:

• dos tests amb tomàquets i un amb flors

This is a very normal kind of ellipsis.

Amb usually means with.

Here it links the pots to what they contain:

• tests amb tomàquets = pots with tomatoes
• un amb flors = one with flowers

So amb is functioning just as with does in English.

Because Catalan often omits the article when talking about the contents or type of something in a general way.

So:

• tests amb tomàquets = pots with tomatoes
• un amb flors = one with flowers

If you added articles, the meaning could become more specific depending on context, but in this sentence the bare nouns sound natural and general.

Yes, Catalan word order is somewhat flexible.

These are both natural:

• Al pati de la meva tieta hi ha dos tests...
• Hi ha dos tests... al pati de la meva tieta

The version in your sentence puts Al pati de la meva tieta first to set the scene: In my aunt’s patio...

That is very common in Catalan.

The accent mark shows the stress.

• tomàquet
• tomàquets

The à tells you the stress falls there. Accent marks in Catalan are important because they help indicate pronunciation and sometimes distinguish words.

So even if you already know the meaning, the accent is a useful pronunciation guide.