Learn Hardcore Spanish (Spain): Cuando vuelva a la ciudad, estaré muy agradecida por cada recuerdo de este campo tranquilo. - When I return to the city, I will be very grateful for each memory of this peaceful countryside.

Cuando vuelva a la ciudad = When I return to the city (in the future)
The action of volver hasn’t happened yet and is seen as uncertain/not completed ⇒ subjunctive: vuelva.
The main clause is in the future (estaré), so the time clause with cuando takes the present subjunctive.

You would not say cuando volveré a la ciudad in standard Spanish in this structure; that sounds wrong to native speakers. The pattern is:

Cuando + present subjunctive, future (or ir a + infinitive) in the main clause.

Why is the verb in the main clause estaré (future) and not present, like estoy muy agradecida?

Estaré muy agradecida focuses on a feeling you will have later, at the time you’re back in the city.

Compare:

Cuando vuelva a la ciudad, estaré muy agradecida…
= At that future moment, I will feel very grateful.
Cuando vuelva a la ciudad, estoy muy agradecida…
sounds wrong, because it mixes a future time reference (cuando vuelva) with a present feeling (estoy).

You could also say:

Cuando vuelva a la ciudad, voy a estar muy agradecida…
This is also correct; it uses the ir a + infinitive future instead of the simple future, with a similar meaning.

Why is it agradecida with an -a at the end? Who is grateful?

Agradecida agrees in gender with the implied subject of the sentence.

The full idea is: (Yo) estaré muy agradecida…
Since the adjective is agradecida (feminine), the speaker is a woman (or someone choosing feminine grammatical gender).
If the speaker were male, it would be:
Cuando vuelva a la ciudad, estaré muy agradecido por cada recuerdo…

In Spanish, adjectives must agree in gender and number with the subject:

agradecido (masculine singular)
agradecida (feminine singular)
agradecidos / agradecidas (plural).

Why do we need the preposition a in cuando vuelva a la ciudad?

In Spanish, movement towards a place normally uses a:

volver a la ciudad = to return to the city
ir a la ciudad = to go to the city
llegar a la ciudad = to arrive in/at the city

Without a, volver la ciudad would be incorrect, because volver needs a preposition before the destination.

Why is it por cada recuerdo and not para cada recuerdo?

With estar agradecido/a, the standard preposition is por:

estar agradecida por algo = to be grateful for something.

So:

estaré muy agradecida por cada recuerdo
literally = I will be very grateful *for each memory*.

Para here would sound wrong, because para usually introduces a purpose/destination (for someone, for a use), not the cause or reason of a feeling.
The reason or cause of gratitude uses por.

Could I use de or con instead of por after agradecida?

In standard modern usage:

Lo normal is: estar agradecido/a por algo.
Agradecido/a con alguien is also common in many varieties (especially in Latin America):
- Estoy agradecida con mis padres. = I’m grateful to my parents.
Sometimes you’ll see agradecido/a de in specific expressions, but it’s much less common and can sound more old-fashioned or regional.

In your sentence, the most natural and neutral version is:

estaré muy agradecida por cada recuerdo…

Using por is clearly correct and the safest choice.

Why is recuerdo used here and not memoria?

Both can relate to “memory,” but they’re used differently:

recuerdo = a specific memory or souvenir (a thing you remember, or even an object you keep).
- cada recuerdo de este campo tranquilo = each memory of this peaceful field.
memoria = the faculty of memory (your ability to remember) or, in some contexts, a more formal/abstract “remembrance.”
- Tengo buena memoria. = I have a good memory (ability).
- En memoria de… = In memory of…

In your sentence, we’re talking about individual remembered experiences, so recuerdo is the natural choice.

Why does the adjective come after the noun: campo tranquilo and not tranquilo campo?

In Spanish, descriptive adjectives normally go after the noun:

campo tranquilo = a peaceful/quiet field.

If you put the adjective before the noun, it usually sounds:

more poetic, emotional, or literary, or
it slightly changes the nuance (often making it more subjective).

So:

tranquilo campo might appear in poetry or very literary language, but in normal, everyday Spanish, you say campo tranquilo.

What is the difference between este campo tranquilo and just este campo or el campo tranquilo?

Each option adds or removes information:

este campo tranquilo
- este: this field (physically or mentally close to the speaker)
- tranquilo: explicitly says it is peaceful/quiet.
este campo
- Just “this field” — no explicit mention of quietness.
el campo tranquilo
- “the peaceful/quiet field,” but without the sense of closeness that este gives; it’s more neutral or just “that specific field we both know about.”

So este campo tranquilo combines:

specific reference (este)
plus a descriptive quality (tranquilo).

Can I change the order of the clauses, like: Estaré muy agradecida por cada recuerdo de este campo tranquilo cuando vuelva a la ciudad?

Yes, you can swap the order:

Cuando vuelva a la ciudad, estaré muy agradecida…
Estaré muy agradecida… cuando vuelva a la ciudad.

Both are grammatically correct and natural.

Notes:

When the cuando-clause comes first, it’s usually followed by a comma.
When it comes second, the comma is often omitted in normal writing.

So your alternative version is fine:

Estaré muy agradecida por cada recuerdo de este campo tranquilo cuando vuelva a la ciudad.