Learn Hardcore Turkish: Bulaşık süngerini değiştirip tezgâhı güzelce sildim. - I replaced the dish sponge and wiped the counter nicely.

No. Here it comes from the compound noun bulaşık süngeri (“dish sponge”). In Turkish indefinite noun compounds, the second noun takes a 3rd person possessive marker as a compound marker: bulaşık sünger-i. Then we add the accusative for definiteness: bulaşık sünger-i-(n)i → bulaşık süngerini. So it means “the dish sponge” (as a specific, known one), not “his/her sponge.”

Why does the second word in bulaşık süngeri have -i on it?

That’s the standard pattern for an indefinite noun–noun compound (belirtisiz isim tamlaması): first noun bare, second noun with the 3rd person possessive suffix. Examples:

okul çantası “school bag”
mutfak havlusu “kitchen towel”
bulaşık süngeri “dish sponge”

What’s the extra -n- in süngerini?

It’s the buffer consonant used before the accusative when the word already ends in a vowel (and especially when a possessive/compound suffix is present). Pattern:

sünger-i (compound) + (n)i (accusative) → süngerini Compare: çanta → çantayı (buffer -y- after a bare vowel), but çantası → çantasını (buffer -n- after a possessive).

Why are both objects marked with the accusative: bulaşık süngerini and tezgâhı?

In Turkish, definite/specific direct objects take the accusative. Here, both items are specific and known from context (the dish sponge in the kitchen; the counter), so they’re accusative. If you drop accusative, the meaning becomes indefinite:

Bulaşık süngeri değiştirip tezgâh sildim. “I changed a dish sponge and wiped a counter.” (odd in context)

What does the suffix -ip in değiştirip do? How is it different from ve (“and”)?

The converb -(y)Ip links actions done by the same subject, often read as “and (then).” It’s tighter and more natural than using ve with two full finite verbs.

With -ip: Bulaşık süngerini değiştirip tezgâhı sildim.
With ve: Bulaşık süngerini değiştirdim ve tezgâhı sildim. (also fine) You don’t use both together: not …değiştirip ve…

Does -ip imply sequence (“after”)?

Usually yes; it often suggests the first action precedes the second, but it’s a light, narrative “and (then).” If you want to state “after” explicitly, use:

…değiştirdikten sonra… = “after changing…”
…değiştirince… = “when(ever) I changed…” Example: Bulaşık süngerini değiştirdikten sonra tezgâhı güzelce sildim.

Could I use değiştirerek instead of değiştirip?

Not here. -erek/-arak expresses manner or simultaneity (“by doing X”), so değiştirerek tezgâhı sildim would mean “I wiped the counter by changing (the sponge),” which is odd. Use -ip for sequential coordination.

Why is it tezgâhı with -ı (not -i)?

Accusative vowels follow 4-way vowel harmony. The last vowel of tezgâh is a back vowel (â behaves like a back “a”), so we use the back, unrounded accusative: -ı → tezgâh-ı.

Do I have to write the circumflex in tezgâh? How do I pronounce it?

Spelling: You’ll see both tezgâh and tezgah; the circumflex (â) is optional in everyday writing but preferred in careful writing/dictionaries.
Pronunciation: tez-gâh with a slightly lengthened “a” (like “gaah”), and the final h is pronounced. There is no soft g (ğ) in this word.

How is güzelce different from just güzel?

güzelce is the adverbial form with -ce, meaning “nicely/properly/thoroughly.” In casual speech, güzel can also act adverbially (“well”), but güzelce is clearer as an adverb of manner. A near-synonym is iyice (“thoroughly, really well”):

Tezgâhı güzelce/iyice sildim.

Where can I place güzelce in the sentence?

Default is right before the verb it modifies:

Tezgâhı güzelce sildim. (most natural) You can front it for emphasis: Güzelce tezgâhı sildim, but it’s less common. Keeping it next to the verb avoids ambiguity.

Do I need to say ben?

No. The ending -dim on sildim already marks 1st person singular past (“I wiped”). You’d add ben only for emphasis or contrast: Ben sildim.

Could bulaşık süngeri be understood as “dirty sponge”?

In isolation, bulaşık can mean “dirty,” but in this set phrase bulaşık süngeri is a lexicalized compound meaning “dish sponge” (the sponge used for washing dishes). Context strongly favors that reading.

What’s the full morphological breakdown?

bulaşık sünger-i-(n)i = dish sponge + compound marker (3sg poss) + accusative
değiştir-ip = change + converb “and (then)”
tezgâh-ı = counter + accusative
güzel-ce = nice + adverbial suffix
sil-di-m = wipe + past + 1sg Overall: “(Having) changed the dish sponge, I wiped the counter thoroughly.”

What’s the difference between değişmek and değiştirmek?

değişmek = to change (intransitive): Sünger değişti. “The sponge changed.”
değiştirmek = to change/replace (transitive): Süngeri değiştirdim. “I changed/replaced the sponge.”