Wewe unafanya kazi ofisini kila siku.

Break unafanya into three morphemes: • u- = second-person singular subject (“you”)
• -na- = present-tense/aspect marker (“now” or ongoing)
• fanya = verb root “do/make.”
Together: u + na + fanya = “you do/make,” so in context unafanya kazi = “you work.”

Yes. Kufanya is a transitive verb meaning “to do/make.” Kazi (“work”) is its direct object:
kufanya kazi = “to do work” → “to work.”
If you said just unafanya, listeners would expect you to specify what you’re doing.

Ofisi means “office.” Adding the locative suffix -ni turns it into “in/at the office.” This is a common way in Swahili to say “at/in [place]” without a separate preposition. So:
ofisi + ni → ofisini = “in/at the office.”
Alternatives include katika ofisi or kwenye ofisi, but ofisini is more concise.

Kila means “each” or “every” and must pair with a singular noun. Thus kila siku literally “each day” = “every day.”
If you want “all days,” you’d use the plural with zote, e.g. siku zote = “all days.”

For a yes/no question, you can start with Je and keep the verb unchanged:
Je, unafanya kazi ofisini kila siku?
In casual speech you can drop Je and rely on intonation:
Unafanya kazi ofisini kila siku?

Change the subject prefix u- (“you”) to ni- (“I”):
Nafanya kazi ofisini kila siku.
Optionally add mimi for emphasis: Mimi nafanya kazi ofisini kila siku.

Use the negative present tense prefix hu- and change the final -a of the verb to -i:
Haufanyi kazi ofisini kila siku.

• u-na-fanya is the simple/present progressive: “you are doing/you do.”
• hu-fanyi is the habitual present: “you usually/regularly do.”
  Both can express “you work,” but hufanyi kazi kila siku stresses the habitual aspect (“you habitually work every day”) while unafanya is more neutral/present. With time words like kila siku, speakers commonly use either.