Learn Hardcore Esperanto: Hodiaŭ mi iras laŭ trankvila strato al la oficejo. - Today I go along a quiet street to the office.

iras is just “go” in present tense. Context decides whether you understand it as “I go” (habitually) or “I am going” (right now).
Hodiaŭ mi iras… in normal conversation is understood as “Today I’m going…” (today’s concrete plan).
Forms like estas iranta exist but are rarely needed; they explicitly emphasize the ongoing process (“am in the middle of going”), and often sound unnatural where English requires a continuous form.

Could I also say Hodiaŭ mi iros laŭ trankvila strato al la oficejo? What’s the difference between iras and iros here?

Yes, you can say that, but the meaning changes slightly:

Hodiaŭ mi iras… – usually implies a planned or ongoing action today; very natural if you’re about to leave, or describing what you’re doing today.
Hodiaŭ mi iros… – uses the future (iros) and puts a bit more focus on the fact that this is something that will happen later today, more like a plan or prediction.

Both are grammatically correct. Use:

iras when the action is part of today’s arrangements or is already underway.
iros when you want to highlight it as a future event within today.

What exactly does laŭ mean in laŭ trankvila strato? How is it different from sur or from laŭ mi (“according to me”)?

laŭ has two common uses:

Spatial: “along”
- laŭ trankvila strato = along a quiet street, following the street’s course.
- It indicates movement parallel to or following something:
  - iri laŭ la rivero – go along the river.
Non‑spatial: “according to”
- laŭ mi – according to me
- laŭ la raporto – according to the report

So context tells you whether it’s “along” or “according to”.

sur, by contrast, means “on” (on top of, on the surface of):

sur la strato – on the street (physically located on it), but not specifically “along” its length.
iri laŭ la strato focuses on following the street;
iri sur la strato just places you on the street.

Why doesn’t strato take -n (accusative) in laŭ trankvila strato, even though there is motion?

You don’t use the accusative -n when a preposition already expresses direction clearly.

laŭ trankvila strato – “along a quiet street”
The preposition laŭ already tells us how you move relative to the street, so no -n.

Compare:

Mi iras la straton. – I go (along / up) the street.
Here no preposition, so la straton takes -n to show the direction.
Mi iras en la oficejon. – I go into the office.
en can be static (in) or directional (into), so -n on oficejo marks that it’s into.

Rule of thumb:
If the preposition itself unambiguously shows direction (al, el, ĝis, tra, laŭ, etc.), you normally don’t add -n to the noun after it.

Why is it trankvila strato and not trankvilo strato? How does adjective agreement work here?

In Esperanto:

Adjectives end in -a.
Nouns end in -o.

So:

trankvila – quiet (adjective)
strato – street (noun)
Together: trankvila strato – quiet street.

Adjectives agree with the noun in:

Number:
- trankvila strato – a quiet street
- trankvilaj stratoj – quiet streets
Case (if accusative is used):
- Mi promenas laŭ trankvilan straton. – I walk along a quiet street.
  (Here both trankvilan and straton take -n.)

In your sentence, since strato isn’t accusative, the adjective is just trankvila (singular, non‑accusative).

Why is there no article before trankvila strato, but there is an article before oficejo (al la oficejo)?

The definite article la means roughly “the (specific one you have in mind)”.

la oficejo – the office (a specific office, usually my office / our office / the one known from context).
trankvila strato without la is more indefinite / generic: “a quiet street” (no specific one previously identified in the conversation).

You could say:

Hodiaŭ mi iras laŭ la trankvila strato al la oficejo.
That would imply a particular quiet street already known to both speaker and listener.

So in the original:

The office is a known, specific place → la oficejo.
The street is just described as some quiet street on the way → no article.

Could I say Hodiaŭ mi iras la oficejon instead of al la oficejo? What’s the difference between using al and just the accusative?

Yes, Hodiaŭ mi iras la oficejon is grammatically correct, but al la oficejo is more common and neutral.

iri al la oficejo – go to the office
Uses the preposition al = to, toward. Very straightforward and widely used.
iri la oficejon – literally go (taking as direction) the office.
Here the -n on oficejo shows destination without a preposition.

Both are understandable. Style notes:

Using al is usually clearer and more idiomatic, especially for beginners.
Using the naked accusative of direction (without al) can feel a bit more literary or compact, and is used more in written or somewhat elevated style.

What does the suffix -ejo in oficejo mean? How is oficejo different from something like ofico?

The suffix -ejo means “place associated with X”.

ofico – an office in the sense of a post, position, function (e.g. a public office, a role).
oficejo – the place where office work happens: an office (room / workplace).

Other examples of -ejo:

lerni (to learn) → lernejo – school (place to learn)
preĝi (to pray) → preĝejo – church (place to pray)
hospitalo already has -o as a root, but banejo from bani (to bathe) – bathhouse.

So oficejo specifically refers to the physical place / building / room where the office work is done.

How free is the word order here? Can I say Mi hodiaŭ iras laŭ trankvila strato al la oficejo or Mi iras al la oficejo laŭ trankvila strato hodiaŭ?

Esperanto word order is relatively flexible, especially compared with English. All of these are grammatical:

Hodiaŭ mi iras laŭ trankvila strato al la oficejo.
Mi hodiaŭ iras laŭ trankvila strato al la oficejo.
Mi iras hodiaŭ laŭ trankvila strato al la oficejo.
Mi iras laŭ trankvila strato al la oficejo hodiaŭ.

Differences are mostly about emphasis and flow, not basic meaning:

Putting hodiaŭ first (Hodiaŭ mi iras…) highlights “today”.
Putting al la oficejo earlier might emphasize the destination, etc.

Because endings (like -as, -o, -a, -n) show grammatical roles, word order can move around more freely. However, a fairly “English-like” order (Hodiaŭ mi iras…) is very common and clear.

Is there any difference between Hodiaŭ mi iras laŭ trankvila strato al la oficejo and Hodiaŭ mi iras al la oficejo laŭ trankvila strato?

No real difference in basic meaning; both say you’re going to the office along a quiet street today.

Subtlety:

…laŭ trankvila strato al la oficejo. – slightly more linear “route then destination” feeling.
…al la oficejo laŭ trankvila strato. – may sound a bit more like the destination is mentioned first, then you add how you get there.

In everyday use, both are perfectly natural and equivalent; context and intonation carry any fine shades of emphasis.