Pestyäni pyykit pesutuvassa menin suoraan saunaan rentoutumaan.

Pestyäni is a special Finnish verb form often called a temporal construction. It means something like after I had washed or once I washed/had washed.

It contains both:

• the idea of the action being completed first, and
• the subject I

So Finnish does not need a separate word like after here.

Breakdown:

• pestä = to wash
• pestyä- = a form meaning having washed / after washing
• -ni = my / I here, showing that I am the one who did it

So Pestyäni pyykit... means After washing the laundry...

The ending -ni is a possessive suffix, but in this structure it tells you who did the action. Here it means the subject is I.

Compare:

• pestyäni = after I had washed
• pestyäsi = after you had washed
• pestyään = after he/she had washed

This is one reason Finnish can leave out the pronoun minä.

Because Finnish usually does not need subject pronouns when the verb form already shows the person.

Here you can see I in two places:

• pestyäni → -ni tells us the washing was done by me
• menin → the ending -n means I went

So adding minä would usually be unnecessary unless you want extra emphasis.

Because pyykit is the total object here: the laundry was washed as a completed whole.

Finnish often marks the object differently depending on whether the action is:

• complete / result reached → total object
• ongoing / incomplete / part of something → partitive

So:

• Pestyäni pyykit = after I washed all the laundry / the laundry batch
• Pesin pyykkiä = I was washing laundry / I washed some laundry

Also, pyykit is very natural in Finnish when talking about a batch of laundry or clothes.

Pesutuvassa is in the inessive case (-ssa / -ssä), which usually means in or inside something.

• pesutupa = laundry room / communal washroom
• pesutuvassa = in the laundry room

So Pestyäni pyykit pesutuvassa... means After washing the laundry in the laundry room...

It tells you the location where the washing happened.

Because the sentence describes movement into the sauna.

• sauna = sauna
• saunaan = into the sauna
• saunassa = in the sauna

Since the speaker went there, Finnish uses the illative case:

• menin saunaan = I went into the sauna

If the sentence were about being there, it would use saunassa:

• olin saunassa = I was in the sauna

Because after a verb of motion like mennä (to go), Finnish often uses the third infinitive illative to show purpose.

So:

• mennä rentoutumaan = to go to relax
• literally: go into relaxing

Breakdown:

• rentoutua = to relax
• rentoutumaan = to go in order to relax

This is a very common pattern:

• mennä syömään = go eat
• mennä nukkumaan = go to sleep
• mennä opiskelemaan = go study

Suoraan means straight, directly, or without stopping anywhere else first.

So:

• menin suoraan saunaan = I went straight to the sauna

It gives the sense that after washing the laundry, the speaker did not do something else in between.

No, Finnish word order is quite flexible. But putting Pestyäni pyykit pesutuvassa first is very natural because it sets the time background first: after doing X, I did Y.

This order is especially common when:

• one action happened first
• the next action is the main point

A different order is possible, but this version sounds smooth and natural.

Yes. In this kind of structure, the subject of pestyäni is normally the same as the subject of the main verb.

So here the sentence means:

• I washed the laundry
• I went straight to the sauna

If the subjects were different, Finnish would usually use a different structure, often a full clause such as kun + verb.

Yes. A more explicit version would be:

Kun olin pessyt pyykit pesutuvassa, menin suoraan saunaan rentoutumaan.

That means the same thing: When/after I had washed the laundry in the laundry room, I went straight to the sauna to relax.

The difference is mainly style:

• Pestyäni... = more compact, somewhat more written or polished
• Kun olin pessyt... = more straightforward and often easier for learners

Both are correct.

Because the opening part Pestyäni pyykit pesutuvassa functions like an introductory time clause or time phrase.

Finnish normally separates that kind of fronted background element from the main clause with a comma:

• Pestyäni pyykit pesutuvassa, menin...

This is similar to English punctuation in sentences like:

• After washing the laundry, I went...