Learn Hardcore Swahili: Geuza kiti hiki kidogo, kisha kaa pembeni ya dirisha. - Turn this chair a little, then sit beside the window.

As an adverb meaning “a little/briefly/slightly,” it modifies the verb: most speakers will read Geuza kiti hiki kidogo as “Turn this chair a little.”
As an adjective meaning “small,” it would describe the noun: kiti hiki kidogo can also mean “this small chair.”

To make the “a little” meaning crystal clear, you can say:

Geuza kidogo kiti hiki, or
Use an object marker: Kigeuze kidogo (“Turn it a little”).

To clearly mean “this small chair,” you could say:

Geuza kiti hiki kidogo sana (this small chair, with emphasis), or rearrange: Geuza hiki kiti kidogo (more emphatic “this chair (which is small)”).

Why does the demonstrative hiki come after kiti (not before it)?

In Swahili the default position of the demonstrative is after the noun: kiti hiki (“this chair”). You can put it before for emphasis or contrast, e.g., hiki kiti (“this chair (not that one)”), but post-nominal is the unmarked choice.

Which noun class is kiti, and how does that affect agreement?

Kiti is class 7 (Ki-/Vi-), plural viti (class 8). That affects:

Demonstratives: hiki (this), hicho (that near you), kile (that over there); plural hivi, hivyo, vile.
Object markers: singular ki-, plural vi-. So “Turn it (the chair)” can be Kigeuze, and “Turn them (the chairs)” can be Vigeuze (often you’ll just say the noun: Geuza viti).

What’s the difference between geuza and geuka?

Geuza is transitive: “turn/convert/change something” (you act on an object). Example: Geuza kiti (“Turn the chair”).
Geuka is intransitive: “turn/transform oneself/become.” Example: Kiti kimegeuka (“The chair has turned/changed (by itself)”).

How do I say “Turn it a little” using an object marker?

Use the class 7 object marker ki- with the imperative, and the final vowel changes to -e: Kigeuze kidogo.

Without the object marker: Geuza kidogo kiti hiki.
With the object marker (no need to repeat the noun): Kigeuze kidogo.

How do I address more than one person?

Use the plural imperative -ni:

Geuzeni kiti hiki kidogo, kisha kaeni pembeni ya dirisha. You can also use ketini instead of kaeni (see next question).

Is there a difference between kaa and keti?

Yes:

Kaa means “sit,” but also “stay/live/remain.” It’s very common in speech. “Sit down” is often kaa chini (literally “sit down/low”).
Keti specifically means “to sit (be seated)” and sounds a bit more formal/bookish. Imperatives: keti (sg.), ketini (pl.).

In your sentence, kaa is perfectly natural.

What exactly does pembeni ya dirisha mean? Is it “by,” “beside,” or “next to”?

Pembeni ya X means “at the side/edge of X,” usually understood as “beside/next to X.” So pembeni ya dirisha is “next to the window / by the window.”

Could I use other ways to say “by the window,” like kando ya, karibu na, or -ni?

Yes, with slight nuances:

kando ya dirisha: alongside/by the side of the window (very close, similar to pembeni ya).
karibu na dirisha: near the window (close, but not necessarily right next to it).
dirishani: using the locative -ni: “at the window” (very idiomatic). All are good; choose based on how close you want to sound.

Why is it pembeni ya dirisha and not something like pembeni la/cha dirisha?

Many locative adverbs/prepositions in Swahili take a fixed ya (or sometimes na) regardless of the noun class of the following noun. Examples: nyuma ya, mbele ya, katikati ya, juu ya, chini ya, pembeni ya. So it’s pembeni ya dirisha by rule, not agreement with dirisha.

Is kisha the only or best way to say “then”?

Kisha is common and slightly formal. Alternatives:

halafu (very common in speech)
baadaye (later, after some time)
Colloquial alafu (informal variant of halafu)

Your sentence works with either kisha or halafu.

If I want to be more polite, how can I soften the imperatives?

Several options:

Add tafadhali: Tafadhali geuza kiti hiki kidogo, kisha kaa pembeni ya dirisha.
Use a polite request with naomba
- subjunctive: Naomba ugeuze kiti hiki kidogo, halafu ukae pembeni ya dirisha.
Use conditional: Ukiacha, geuza kiti hiki kidogo… (context-dependent; often softer in longer instructions).

Is the comma before kisha necessary?

Punctuation is flexible; a comma is natural in English. In Swahili orthography, you’ll often see either a comma or no punctuation: Geuza … kidogo kisha kaa … Both are acceptable; the pause is more about rhythm than strict grammar.

Could I use badilisha instead of geuza?

Only if you mean “change/replace/alter” rather than “turn/rotate/adjust.”

Geuza kiti suggests rotating/repositioning the chair.
Badilisha kiti suggests changing the chair (swap it out) or changing something about it—not just turning it slightly.