Learn Hardcore Swahili: Juma alijuta kutofanya nakala ya faili yake jana. - Juma regretted not making a copy of his file yesterday.

Present (habitual/progressive): anajuta — “he/she regrets / is regretting”
Present perfect: amejuta — “he/she has regretted (and the result is relevant now)”

What exactly is kutofanya and how is it formed?

It’s the negative infinitive/gerund: kuto- + verb stem, meaning “not to do / not doing.” Examples:

kutosoma = not to read
kutokwenda = not to go
kutokula = not to eat
In this sentence: kuto-
- fanya → kutofanya (“not to do/make”)

You may also see forms like kutokufanya in real-world writing; kutofanya is shorter and widely preferred in teaching materials and style guides.

Why use the negative infinitive (kutofanya) instead of a finite negative like hakufanya?

After stance/feeling verbs such as kujuta (to regret), Swahili often uses a nominalized clause (the infinitive) for the thing regretted: alijuta kutofanya... = “he regretted not doing...”.
A finite negative is also possible if you introduce a subordinate clause (see next Q).

Can I say Juma alijuta kwamba hakufanya nakala... instead?

Yes: Juma alijuta kwamba hakufanya nakala... is perfectly good.

alijuta kutofanya... treats “not doing X” as a general action/idea.
alijuta kwamba hakufanya... presents a specific past fact (“that he didn’t do X”).
Both are natural; the infinitive is a bit more compact.

In nakala ya faili yake, why is the connector ya used and not wa/la/cha?

Ya is the associative connector (“of”) that agrees with the head noun nakala. Nakala is class 9 (N-class), which takes ya in the singular. If it were plural (“copies”), you’d use class 10: nakala za...

What noun classes are nakala and faili, and how do they affect yake?

nakala is N-class (9/10).
faili varies in usage: many speakers treat it as N-class (9/10), others as class 5/6 (singular faili, plural mafaili).
In this sentence, faili is treated as N-class, so “his/her” is yake (not lake, which would match class 5). You will also encounter faili lake among speakers who put faili in class 5—both patterns occur; just be consistent.

What exactly does yake refer to here? Could it mean someone other than Juma?

Yake agrees with faili and means “his/her/its.” It can refer to Juma or to another person/entity—context decides. To make it explicit, you can say faili la Juma (“Juma’s file”).

Does jana (“yesterday”) modify the regretting or the not-copying?

As written, jana at the end most naturally attaches to the nearer action—“not making a copy.”
To say he regretted yesterday (regret time), place jana early: Jana Juma alijuta...
To say the copying failed yesterday (action time), keep jana near the infinitive or object: ...kutofanya nakala ya faili yake jana.

Is kufanya nakala idiomatic, or should I use kunakili?

Both are fine, with slight nuances:

kufanya nakala (ya X) = “to make a copy (of X)” (very natural in everyday Swahili)
kunakili X = “to copy X” (common in school/office/IT contexts) Either works here: kufanya nakala ya faili or kunakili faili.

Could I drop the name and just say Alijuta kutofanya...?

Yes. The subject prefix a- already means “he/she.” However, without Juma (or context) it’s ambiguous who “he/she” is.

How would I say “Juma regrets (now) not having made a copy yesterday”?

Use the present perfect: Juma amejuta kutofanya nakala ya faili yake jana.

If there were multiple files, how would that change?

If you keep faili in N-class (9/10): nakala ya faili zake = “a copy of his files” (possessive plural: zake).
If you use class 5/6: nakala ya mafaili yake/lake (both are heard; yake if you treat mafaili as 6 taking “ya-/za-” patterns in some dialects, lake would match singular class 5, so for plural class 6 you’d typically use yake/zao depending on what you’re agreeing with). In practice, speakers vary; the safest is to keep both nouns in the same class system consistently, e.g., N-class: faili zake; 5/6-class: mafaili yake.

Should kuto- be written together with the verb or separately (e.g., kuto fanya)?

Together. It’s written as one word with the verb: kutofanya, kutosoma, kutokwenda, kutokula (no space).

How would I negate the main verb instead (e.g., “Juma didn’t regret not making a copy”)?

Use negative past on the main verb: Juma hakujuta kutofanya nakala ya faili yake jana.