Vein sekajätteen jäteasemalle, koska talon roskis oli täynnä.

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

• viedä = to take, carry, bring away
• vien = I take / I bring
• vein = I took

In this sentence, vein means I took or I carried. Finnish uses viedä when something is moved away to another place.

A useful contrast:

• viedä = take something there
• tuoda = bring something here

Finnish often leaves out subject pronouns when they are clear from the verb ending.

• vein already means I took
• so minä is not necessary

You could say Minä vein sekajätteen jäteasemalle, but that would sound more emphatic, like I took it.

This is very normal in Finnish:

• Menen kotiin = I’m going home
• Söin jo = I already ate

Because sekajätteen is the object form used here for a completed whole object.

The basic dictionary form is:

• sekajäte = mixed waste

In this sentence, the speaker took the whole load / the specific mixed waste, and the action is complete, so Finnish uses the total object form:

• sekajätteen

For many learners, the easiest practical rule is:

• -n form for a completed whole object
• partitive for an incomplete, ongoing, or unspecified amount

So:

• Vein sekajätteen jäteasemalle = I took the mixed waste to the waste station
• Vein sekajätettä... would suggest some amount of mixed waste, not a complete whole

Technically, this form looks like the genitive singular, and in this kind of sentence it is also the form used for the singular total object.

The ending -lle is the allative case, which often means onto, to, or to the vicinity of something.

So:

• jäteasema = waste station / recycling center
• jäteasemalle = to the waste station

This is the natural choice when talking about going or taking something to a place like this.

A few similar examples:

• kaupalle = to the store
• asemalle = to the station
• pihalle = to the yard

Good question. Both -lle and -an/-en/-iin type endings can express movement toward a place, but they give slightly different images.

• jäteasemalle = to the waste station, as a destination or facility
• jäteasemaan = into the waste station

With jäteasema, Finnish usually prefers jäteasemalle, because the place is thought of more like an area, site, or service point, not mainly as the inside of a building.

So jäteasemalle sounds the most natural here.

Talon is the genitive form of talo.

• talo = house / building
• talon = the house’s / the building’s

So:

• talon roskis = the house’s bin / the building’s trash bin

In natural English, this often means the apartment building’s trash bin or the household bin, depending on context.

The important grammar point is:

• talon tells you whose bin it is
• roskis is the main noun

This is a very common Finnish structure:

• auton ovi = the car’s door
• lapsen kirja = the child’s book
• talon roskis = the building’s bin

Because roskis is the subject of the second clause:

• talon roskis oli täynnä
• the building’s bin was full

In Finnish, the subject is normally in the basic form here, so:

• roskis = subject
• talon = genitive modifier

If roskis were doing a different job in the sentence, its form might change. But here it is simply the thing that was full.

No, roskis is colloquial / everyday Finnish.

It is very common in speech and informal writing, and many Finns use it naturally all the time. Depending on context, it can mean:

• trash can
• garbage bin
• dumpster

More formal or neutral words include:

• roska-astia
• jäteastia
• roskakori (often a smaller trash can)

So this sentence sounds natural and everyday, not especially formal.

Because the sentence is talking about a past situation.

• on = is
• oli = was

So:

• talon roskis on täynnä = the building’s bin is full
• talon roskis oli täynnä = the building’s bin was full

The first clause is also in the past:

• vein = I took

So the tense is consistent across the whole sentence.

Täynnä means full in the expression olla täynnä = to be full.

So:

• roskis oli täynnä = the bin was full

Learners often notice that täynnä does not behave exactly like a simple basic-form adjective such as iso or pieni. The most useful thing to remember is that olla täynnä is a very common fixed expression.

If you want to say what something is full of, Finnish often uses the partitive after täynnä:

• Roskis oli täynnä roskia = The bin was full of trash
• Huone oli täynnä ihmisiä = The room was full of people

In your sentence, that extra part is just omitted because full alone is enough.

Because koska introduces a subordinate clause, and Finnish normally separates that from the main clause with a comma.

So the structure is:

• Vein sekajätteen jäteasemalle = main clause
• koska talon roskis oli täynnä = subordinate clause

This comma is standard Finnish punctuation.

Yes. Finnish word order is fairly flexible.

You can also say:

• Koska talon roskis oli täynnä, vein sekajätteen jäteasemalle.

That means the same thing: Because the building’s bin was full, I took the mixed waste to the waste station.

The version with vein first is very natural when the speaker starts with the main action.
The version with koska first puts the reason first.

Finnish makes compound nouns very freely, and this sentence has two useful examples.

• sekajäte

  • seka = mixed
  • jäte = waste
  • together: mixed waste

• jäteasema

  • jäte = waste
  • asema = station
  • together: waste station / recycling center

Seeing compounds in parts is very helpful for vocabulary building in Finnish.