Learn Hardcore Croatian: Nakon posla on uvijek spremi posuđe i stavi čiste tanjure na policu. - After work he always puts away the dishes and puts the clean plates on the shelf.

On uvijek spremi posuđe… – normal, slight emphasis on he specifically.
Uvijek spremi posuđe… – also correct; context tells us who spremi refers to.

So you can omit on; using it can emphasize that man / that person rather than someone else.

What does spremi posuđe mean exactly? Is it “wash the dishes”?

Spremi posuđe literally means “put away / tidy up the dishes”, not “wash the dishes”.

oprati posuđe – to wash the dishes
spremiti posuđe – to put the dishes away, clear them, tidy them (e.g. into cupboards)

So the sentence says that after work, he always puts away the dishes and puts clean plates on the shelf – it implies they are already washed.

Why is it spremi and stavi, not sprema and stavlja?

You are seeing the perfective aspect vs imperfective aspect:

spremati / spremiti – to tidy / put away
- sprema = he is tidying / he tidies (imperfective)
- spremi = he will tidy / he tidies (as a single completed action) (perfective)
stavljati / staviti – to put, to place
- stavlja = he is putting / he puts (imperfective)
- stavi = he will put / he puts (as a single completed action) (perfective)

Here, spremi and stavi present the actions as completed each time after work. With uvijek (always), it means that every time this situation happens, he ends up completing these actions.

If you said:

Nakon posla on uvijek sprema posuđe i stavlja čiste tanjure na policu.

…it would sound more like a general habit in progress (more open‑ended), while spremi / stavi feel more like a neatly finished step in the routine. Both versions are possible, with a slight nuance.

Why is posuđe used without a plural? Can you say posuđa?

Posuđe is a collective noun in Croatian. It refers to dishes, crockery, tableware as a group and is usually treated as singular, neuter:

posuđe je čisto – the dishes are clean (literally “the dishes is clean”)

You generally do not use a regular plural like posuđa in everyday language. Instead, if you need to count individual items, you name them:

tanjuri – plates
čaše – glasses
zdjele – bowls

So spremi posuđe means “he puts away the dishes / tableware” as a whole set.

Why is it čiste tanjure and not čisti tanjuri?

The phrase čiste tanjure is in the accusative plural because it is the direct object of the verb stavi (he puts):

tanjur – plate (masculine, nominative singular)
tanjuri – plates (masculine, nominative plural)
tanjure – plates (masculine, accusative plural, inanimate)

Adjectives must agree in case, number, and gender:

čisti tanjuri – clean plates (nominative plural, subject)
čiste tanjure – clean plates (accusative plural, object)

Since we are saying “he puts clean plates on the shelf,” čiste tanjure (accusative) is correct.

Why is it na policu and not na polici?

With na, Croatian distinguishes between:

Motion toward / onto something → accusative
- na policu – onto the shelf
Location (being on something) → locative
- na polici – on the shelf (static location)

In this sentence, stavi čiste tanjure na policu describes putting the plates onto the shelf (movement), so you use the accusative: policu.

If you were just describing where the plates already are, you’d use the locative:

Čisti tanjuri su na polici. – The clean plates are on the shelf.

What is the base form of posla and policu, and what cases are they?

posla
- Base form (nominative): posao – work, job
- Here: genitive singular after nakon → nakon posla (after work)
policu
- Base form (nominative): polica – shelf
- Here: accusative singular after motion na → na policu (onto the shelf)

Can I change the word order, for example On nakon posla uvijek spremi posuđe…?

Yes, Croatian word order is relatively flexible, though some orders sound more natural than others.

Common, very natural orders would be:

Nakon posla on uvijek spremi posuđe…
Nakon posla uvijek spremi posuđe…
On nakon posla uvijek spremi posuđe… – also possible, mild emphasis on on.

What usually stays together are verb + its objects:

spremi posuđe
stavi čiste tanjure na policu

Moving adverbs and phrases like nakon posla and uvijek mostly affects emphasis, not grammar.

Is uvijek always placed before the verb like in on uvijek spremi?

Uvijek (always) most often comes before the verb in neutral sentences:

On uvijek spremi posuđe.

Other positions are possible for emphasis:

Uvijek on spremi posuđe. – Emphasis on he in contrast to others.
On posuđe uvijek spremi. – Stronger emphasis on he definitely always does it, slightly marked.

In your sentence, on uvijek spremi is the most neutral and natural placement.