Minha prima tirou outra foto da ponte na quarta-feira à tarde.

Because minha has to agree with prima, and prima is a feminine noun.

• meu = my, used with masculine singular nouns
• minha = my, used with feminine singular nouns

So:

• meu primo = my male cousin
• minha prima = my female cousin

The possessive agrees with the thing possessed, not with the speaker.

Both are possible in Brazilian Portuguese.

• Minha prima tirou...
• A minha prima tirou...

In Brazil, possessives often appear with an article, but leaving the article out is also very natural, especially in simple statements like this one. So minha prima here is completely normal.

Yes. Portuguese usually marks gender in family words more clearly than English does.

• primo = male cousin
• prima = female cousin

English just says cousin, but Portuguese tells you whether the cousin is male or female.

Tirou is the preterite (simple past) form of tirar, for ele/ela/você.

Here it means took:

• ela tirou uma foto = she took a photo

So tirou tells you the action happened and is completed in the past.

This is just the normal expression in Portuguese:

• tirar uma foto
• tirar uma fotografia

Literally, tirar often means things like take out, remove, or take, but in this expression it simply means to take a photo. It is an idiomatic use you just learn as a set phrase.

Because outra by itself can already mean another.

• outra foto = another photo

You can also say uma outra foto, but it is not necessary here. In many cases, Portuguese naturally uses just outro / outra without an article.

So:

• tirou outra foto = took another photo

is the most straightforward way to say it.

Da is a contraction of de + a:

• de
  • a ponte → da ponte

In this sentence, foto da ponte most naturally means a photo of the bridge.

So:

• uma foto da ponte = a photo of the bridge

Depending on context, de can sometimes have other meanings, but here the normal interpretation is that the bridge is what appears in the photo.

Because Portuguese normally uses a preposition where English says on.

• na quarta-feira = on Wednesday

Grammatically, na is a contraction of:

• em
  • a = na

So the structure is basically:

• em a quarta-feira → na quarta-feira

In natural Portuguese, you use na quarta-feira for on Wednesday, especially when referring to a specific Wednesday.

Two separate points:

1. It is hyphenated because that is the standard spelling of Portuguese weekday names like:

   • segunda-feira
   • terça-feira
   • quarta-feira

2. It is not capitalized because in Portuguese, days of the week are normally written in lowercase, unlike in English.

So:

• English: Wednesday
• Portuguese: quarta-feira

À tarde means in the afternoon.

The à is not just a regular accent mark. It shows crase, which is the contraction of two a sounds:

• a preposition a
• plus the feminine article a

So:

• a + a tarde → à tarde

This is a very common time expression, just like:

• à noite = at night / in the evening
• à esquerda = to the left

You should learn à tarde as a fixed expression.

Yes, in Brazilian Portuguese de tarde is also common and natural.

• à tarde = in the afternoon
• de tarde = in the afternoon

In many situations, both work. À tarde often sounds a little more standard or neutral in textbook-style examples, while de tarde is very common in everyday speech in Brazil.

Yes. Portuguese word order is fairly flexible here.

The original sentence is:

• Minha prima tirou outra foto da ponte na quarta-feira à tarde.

But you could also say:

• Na quarta-feira à tarde, minha prima tirou outra foto da ponte.
• Minha prima, na quarta-feira à tarde, tirou outra foto da ponte.

The meaning stays basically the same. Moving the time phrase to the beginning often puts more emphasis on when it happened.