Vein panttipullot kauppaan ja sain niistä muutaman euron takaisin.

Vein is the past tense, 1st person singular form of viedä.

• viedä = to take / carry / bring something somewhere
• vein = I took / I brought

So Vein panttipullot kauppaan means I took the deposit bottles to the store.

A useful comparison:

• mennä = to go
• viedä = to take something somewhere
• tuoda = to bring something here / toward some reference point

So vein is not just I went. It includes the idea of moving something.

Because Finnish very often makes compound words.

• pantti = deposit
• pullo = bottle
• panttipullo = deposit bottle / bottle with a refund deposit
• panttipullot = deposit bottles

This is very normal in Finnish. English often uses separate words where Finnish prefers one compound word.

Here panttipullot is a total object: the speaker took the bottles as a complete set to the store.

• Vein panttipullot kauppaan = I took the deposit bottles to the store
• Vein panttipulloja kauppaan would sound more like I was taking some deposit bottles to the store or I took deposit bottles / some bottles, with a more indefinite or partial feeling

So -t here helps show that the action is seen as completed and directed at a whole, definite group of bottles.

Because kauppaan is the illative form of kauppa, and the illative often means into or to a place.

• kauppa = shop / store
• kaupassa = in the shop
• kauppaan = into the shop / to the shop

So:

• Vein panttipullot kauppaan = I took the deposit bottles to the store

In everyday Finnish, kauppa often means a grocery store or supermarket.

Sain is the past tense, 1st person singular of saada.

• saada = to get / receive
• sain = I got / I received

So:

• sain niistä muutaman euron takaisin = I got a few euros back from them

Niistä means from them here.

It is the elative plural form of ne.

• ne = they / those
• niistä = from them / out of them / about them, depending on context

In this sentence, niistä refers to panttipullot. So the idea is:

• I got a few euros back from them
• in natural English: I got a few euros back for them / from returning them

Finnish often uses this kind of structure even where English might phrase it differently.

Because semantically it makes more sense: the money comes from returning the bottles, not from the store as a place.

So:

• kauppaan = to the store
• niistä = from the bottles

Even though you return them at the store, the refund is understood as coming from those bottles, meaning from the deposit attached to them.

The basic phrase is:

• muutama euro = a few euros

But in this sentence, the phrase is the object of sain, and it is treated as a total, bounded amount. That is why it appears as:

• muutaman euron

So:

• muutama euro = a few euros
• sain muutaman euron = I got a few euros

This is a very common pattern.

Also compare:

• muutamia euroja = some euros / a few euros, but with a more partitive, less bounded feel
• muutaman euron = a few euros, as a complete amount received

Takaisin means back.

So:

• sain ... takaisin = got ... back

In this sentence:

• sain niistä muutaman euron takaisin = I got a few euros back for them

It shows that the money is being returned, not just received for the first time in some unrelated way.

Because Finnish has no articles.

There is no direct equivalent of English a / an / the in normal Finnish grammar. So Finnish leaves that information to context.

For example:

• kauppaan can mean to a store or to the store
• panttipullot can mean deposit bottles or the deposit bottles, depending on context

In this sentence, English naturally uses the store and the deposit bottles, but Finnish does not need separate article words.

Yes. Finnish word order is fairly flexible, and changing it often changes emphasis rather than core meaning.

The sentence as given is very natural and neutral for a short story-like statement:

• Vein panttipullot kauppaan ja sain niistä muutaman euron takaisin.

But other orders are possible, for example:

• Panttipullot vein kauppaan... = emphasizes the bottles
• Kauppaan vein panttipullot... = emphasizes the store
• Sain niistä takaisin muutaman euron. = possible, but less neutral

So the original order is a good standard version to learn.