La meva germana diu que aquell arbre té una branca massa baixa.

In Catalan, possessives normally go together with the definite article:

• la meva germana = my sister
• el meu amic = my friend
• la nostra casa = our house

So Catalan usually says the my sister where English just says my sister.

You may hear shorter forms such as ma germana in some varieties or styles, but la meva germana is the standard, safe form for learners.

Catalan often leaves out subject pronouns because the verb form already shows the person and number. This is called being a pro-drop language.

So:

• La meva germana diu... = My sister says...
• Ella diu... = She says...

Both are possible, but ella is not necessary unless you want emphasis or contrast.

Diu is the third-person singular present of dir, meaning to say.

So:

• jo dic = I say
• tu dius = you say
• ell/ella diu = he/she says

In this sentence, diu refers back to la meva germana, so it means says.

Here que introduces the clause after diu. It works like English that:

• La meva germana diu que... = My sister says that...

In English, that is often omitted:

• My sister says that...
• My sister says...

In Catalan, after verbs like dir, pensar, creure, you normally keep que.

They are both demonstratives:

• aquest = this
• aquell = that

So:

• aquest arbre = this tree
• aquell arbre = that tree

Aquell usually suggests something farther away, often like that tree over there.

Because arbre is a masculine noun in Catalan:

• l’arbre = the tree
• aquell arbre = that tree

The demonstrative has to agree with the noun:

• masculine singular: aquell
• feminine singular: aquella
• masculine plural: aquells
• feminine plural: aquelles

Since arbre is masculine singular, aquell is the correct form.

Because apostrophes in Catalan are mainly used with articles and some pronouns, not with demonstratives like aquell.

So you get:

• l’arbre = the tree
• aquell arbre = that tree

Even though arbre begins with a vowel, aquell stays unchanged.

Té is the third-person singular present of tenir, meaning to have.

The accent is part of the correct spelling:

• té = has
• te = tea

So the accent helps distinguish words and also marks the stressed vowel.

In this sentence:

• aquell arbre té... = that tree has...

Catalan uses tenir very naturally for parts or features belonging to something:

• L’arbre té una branca... = The tree has a branch...
• La casa té tres finestres. = The house has three windows.

This is normal Catalan.

You could also express the idea in other ways, but té is very natural here because the branch is being presented as part of that specific tree.

Massa means too or excessively.

So:

• massa baixa = too low
• molt baixa = very low

That difference matters:

• molt baixa just describes the branch as very low
• massa baixa implies it is lower than it should be

So massa often suggests a problem or excess.

In Catalan, adjectives often come after the noun, especially when they are simple descriptive adjectives.

So:

• una branca baixa = a low branch
• una branca massa baixa = a branch that is too low

That word order is more natural in Catalan than putting the adjective before the noun.

Because baixa has to agree with branca, which is feminine singular.

Agreement here is:

• baix = masculine singular
• baixa = feminine singular
• baixos = masculine plural
• baixes = feminine plural

Since branca is feminine singular, the adjective must be baixa:

• una branca massa baixa

Not naturally in this sentence. The normal order is:

• una branca massa baixa

Putting massa baixa before branca would sound wrong or very unnatural here.

If you wanted a slightly different structure, you could say something like:

• una branca que és massa baixa = a branch that is too low

But the original version is shorter and very natural.