A l'estiu, m'agrada anar a la platja amb la meva filla.

In Catalan, a + [season/time expression] is a very common way to mean in / during that time period.

So:

• A l'estiu = in the summer / in summer
• A l'hivern = in the winter
• A la primavera = in the spring
• A la tardor = in the autumn

Here, a does not literally mean only to. Like many prepositions, it has several uses depending on context.

Also, l'estiu is el estiu contracted because estiu begins with a vowel:

• el estiu → l'estiu

So:

• a + l'estiu = a l'estiu

M'agrada literally means it pleases me.

It is made of:

• m' = to me
• agrada = pleases / is pleasing

This is one of the biggest differences from English. In English, we say:

• I like going to the beach

But in Catalan, the structure is more like:

• Going to the beach pleases me

That is why agrada is in the 3rd person singular here: the thing being liked is anar a la platja.

Because agradar does not work like English to like.

In English:

• I like X

In Catalan:

• X pleases me
• M'agrada X

So you do not usually say that I am the grammatical subject. The thing you like is the subject.

Examples:

• M'agrada la música. = Music pleases me. = I like music.
• M'agrada llegir. = Reading pleases me. = I like reading.
• M'agrada anar a la platja. = Going to the beach pleases me. = I like going to the beach.

Jo agrado would mean something more like I am pleasing / likable, which is not what you want here.

Because the thing that agrada agrees with is the whole infinitive phrase:

• anar a la platja

That entire idea is treated as a single unit, so Catalan uses agrada (singular).

Compare:

• M'agrada anar a la platja. = I like going to the beach.
• M'agraden les platges. = I like beaches.

So:

• agrada → used with a singular idea, an infinitive, or a singular noun
• agraden → used with a plural noun

Catalan often drops a vowel and uses an apostrophe when one word ending in a vowel comes before another word beginning with a vowel.

So:

• me agrada → m'agrada
• el estiu → l'estiu

This is very common in Catalan and helps the language sound smoother.

Other examples:

• t'agrada = you like
• l'amic = the friend
• d'estiu = of summer / summer...

It is something you will see constantly.

Because anar means to go, and when you say where you go, Catalan normally uses a:

• anar a casa = to go home
• anar a Barcelona = to go to Barcelona
• anar a la platja = to go to the beach

So the sentence contains two different a phrases:

• A l'estiu = in summer
• anar a la platja = to go to the beach

They are doing different jobs:

• the first gives the time
• the second gives the destination

Catalan often uses the definite article more naturally than English does.

So when speaking about a common destination or place, Catalan usually says:

• la platja = the beach
• el cinema = the cinema / the movies
• la piscina = the swimming pool

Even when English might sometimes say simply go to the beach, Catalan strongly prefers anar a la platja.

In Catalan, possessives usually take an article:

• la meva filla = my daughter
• el meu fill = my son
• la nostra casa = our house

So unlike English, where we say my daughter, Catalan usually says something closer to the my daughter.

This is completely normal Catalan grammar.

A few family terms can sometimes appear without the article in certain contexts, especially in informal speech or direct reference:

• ma mare
• mon pare

But for standard, neutral Catalan, la meva filla is exactly what learners should expect.

Amb means with.

So:

• amb la meva filla = with my daughter

It tells you who the speaker goes with.

Example patterns:

• Vaig amb els amics. = I’m going with friends.
• Vinc amb tu. = I’m coming with you.
• M'agrada passejar amb el meu gos. = I like walking with my dog.

Yes, Catalan word order is somewhat flexible, especially with time expressions.

The given sentence:

• A l'estiu, m'agrada anar a la platja amb la meva filla.

is very natural because it starts with the time expression A l'estiu.

You could also say:

• M'agrada anar a la platja amb la meva filla a l'estiu.

This is also correct, but it places less emphasis on summer.

So the original version sounds a bit like:

• In summer, I like going to the beach with my daughter.

while the other version is more like:

• I like going to the beach with my daughter in summer.

Both are fine.

Yes, but not in this exact position.

The full form is em, and it becomes m' before a vowel sound.

So:

• Em gusta would not be Catalan, but
• Em diverteix = It amuses me
• Em fa falta = I need it

With agrada, since agrada begins with a vowel, Catalan uses the elided form:

• em agrada → m'agrada

So m'agrada is simply the correct contracted form before a vowel.

Then the verb would usually become plural:

• M'agraden les platges. = I like beaches.

Why?

Because now the subject is a plural noun:

• les platges

Compare:

• M'agrada anar a la platja.
  Here the subject is the infinitive phrase anar a la platja, treated as singular.

• M'agraden les platges.
  Here the subject is the plural noun les platges.

This contrast is very useful when learning agradar.

Because agrada is the present indicative form of agradar.

So:

• m'agrada = I like / it pleases me

If you wanted I would like, Catalan usually uses the conditional:

• m'agradaria = I would like

Compare:

• M'agrada anar a la platja. = I like going to the beach.
• M'agradaria anar a la platja. = I would like to go to the beach.

So the sentence you have is a normal present-tense statement about preference or habit.