Learn Hardcore Esperanto: Mi faras la taskon kun amiko.

There is no difference between I do and I am doing in Esperanto; both are expressed with mi faras. Context usually makes it clear which English form fits best.

Why does taskon end in -n, but amiko does not?

The ending -n shows the accusative case, mainly used for the direct object of a verb.

Mi faras la taskon. – la taskon is the direct object (the thing being done), so it gets -n.
kun amiko – amiko follows the preposition kun (with), so it does not take -n here.

General rule:

Direct object of the verb → add -n (accusative): taskon, libron, amikinon.
Noun after a normal preposition (like kun, en, sur, por) → usually no -n: kun amiko, en domo, por vi (unless you are marking direction with certain prepositions, which is a more advanced topic).

Why do we say la taskon but not la amiko?

Esperanto has only one article: la, which corresponds to English the.

la taskon = the task (a specific, known task)
amiko without la usually means a friend or (some) friend in general, not a particular one the listener already has in mind.

So:

Mi faras la taskon kun amiko.
→ I am doing *the task with a friend.*

If you said kun la amiko, it would sound like with the friend – some specific friend that both speaker and listener know about.

Could I also say Mi faras taskon (without la)? How does the meaning change?

Yes, Mi faras taskon is correct, but the meaning shifts:

Mi faras la taskon.
→ I am doing the task (a particular task that we both know about).
Mi faras taskon.
→ I am doing a task / some task (not specified which one; just one of possibly many).

So adding la makes it specific, just like English the.

How do I say “my task” instead of “the task” here?

You would use the possessive adjective mia and still add the -n for the direct object:

Mi faras mian taskon kun amiko.
= I am doing my task with a friend.

Notice two things:

mia agrees with tasko and becomes mian in the accusative:
- mia tasko (subject form)
- mian taskon (direct object)
Because mia already shows whose task it is, you usually do not use la:
- Common: mian taskon
- la mian taskon is almost never used and sounds wrong in most contexts.

Can I change the word order of this sentence?

Yes. Esperanto word order is quite flexible, because the roles of words are shown by endings (like -n and -j) rather than strict position.

All of these are grammatically correct:

Mi faras la taskon kun amiko. (neutral order)
Kun amiko mi faras la taskon. (slight emphasis on with a friend)
La taskon mi faras kun amiko. (emphasis on the task as opposed to something else)

As long as:

the subject (here: mi) is clear,
the direct object has -n (here: taskon), the sentence will be understandable.

For beginners, it is safest to stick to the neutral SVO order: Mi faras la taskon kun amiko.

Is there a difference in Esperanto between “I do the task” and “I am doing the task”?

No grammatical difference. Both are normally expressed by:

Mi faras la taskon.

Esperanto verbs do not distinguish simple vs. continuous aspect like English does. The same -as ending covers both I do and I am doing. Context (or extra words like nun = now, kutime = usually) will show the nuance:

Mi nun faras la taskon. – I am doing the task now.
Mi ofte faras la taskon vespere. – I often do the task in the evening.

Why is it kun amiko and not kun amikon?

Normally, nouns after prepositions in Esperanto do not take the accusative -n, because the preposition already shows their role.

kun amiko – with a friend (no -n needed)
por amiko – for a friend
en domo – in a house

The accusative -n can sometimes be added after certain prepositions to show direction / movement toward something (e.g. en la domon = into the house), but kun does not express movement, so you just use kun amiko.

Does amiko mean a male friend, a female friend, or just friend?

In modern Esperanto, amiko generally means friend without specifying gender.

If you want to indicate gender explicitly:

amikino – a female friend (root amik-
- feminine suffix -in-
  - -o)
vira amiko – a male friend (literally: a male friend)

So in Mi faras la taskon kun amiko, you are simply saying with a friend, without telling the gender, unless context makes it clear.

Could I use another verb instead of faras here, like “work on”?

Yes, depending on the nuance you want:

Mi faras la taskon kun amiko.
– I do the task with a friend. (neutral, general)
Mi laboras pri la tasko kun amiko.
– I work on the task with a friend. (labori pri is “to work on something”.)
Mi plenumas la taskon kun amiko.
– I carry out / complete the task with a friend. (emphasis on fulfilling/finishing it)

Fari is the most general word for do / make, so it is very common and completely natural in the original sentence.

Can I leave out Mi and just say Faras la taskon kun amiko?

Normally, no. In Esperanto you almost always need to state the subject explicitly.

Mi faras la taskon kun amiko. – correct.
Faras la taskon kun amiko. – sounds incomplete; we do not know who is doing it.

The main regular exception is in imperatives/commands, where the subject vi (you) is often understood:

Faru la taskon! – Do the task!

But in normal statements, you keep mi, vi, li, etc.

How do I make this sentence plural, like “I do the tasks with friends”?

To make nouns plural in Esperanto, you add -j. If a noun is also in the accusative, it becomes -jn.

So:

la tasko → la taskoj (the tasks)
la taskon → la taskojn (the tasks as direct object)
amiko → amikoj (friends)

Your plural sentence:

Mi faras la taskojn kun amikoj.
= I do the tasks with friends.

Notice:

taskojn has -ojn (plural + accusative), because it is the direct object.
amikoj has -oj (plural), but no -n, because it follows the preposition kun.