Ég geng oft framhjá kirkjunni á leiðinni í vinnu á fimmtudögum.

Geng is the 1st person singular present tense of the verb ganga (to walk, go).

So:

• að ganga = to walk / to go
• ég geng = I walk
• þú gengur = you walk
• hann/hún gengur = he/she walks

A learner may expect something closer to ganga, but Icelandic verbs often change their stem in the present tense. So ganga becomes geng- in ég geng.

In Icelandic, adverbs like oft (often) commonly come after the finite verb in a simple main clause.

So:

• Ég geng oft ... = I often walk ...

This is a very normal word order in Icelandic. English learners sometimes want to say something closer to Ég oft geng..., but that sounds wrong in ordinary Icelandic.

Framhjá means past or by, as in moving past something physically.

So:

• ganga framhjá = walk past
• keyra framhjá = drive past

In this sentence:

• Ég geng oft framhjá kirkjunni
  = I often walk past the church

It is a very common word, and it is typically used with the dative case.

Because framhjá takes the dative.

The noun is:

• kirkja = church

Its singular forms are:

• kirkja = nominative
• kirkju = accusative
• kirkju = dative (indefinite)
• kirkjunni = dative definite = the church

So after framhjá, you need the dative, and because the meaning is the church, you get:

• framhjá kirkjunni = past the church

This is one of the most useful things to notice in the sentence: certain prepositions in Icelandic require a specific case.

That ending shows two things at once:

• it is definite (the church)
• it is in the dative singular

For many feminine nouns, the definite dative singular can look like this:

• kirkju = church / a church (dative)
• kirkjunni = the church (dative)

So the ending is not random; it is carrying grammatical information.

Á leiðinni means on the way.

It comes from:

• leið = way, route, path
• á leiðinni = literally something like on the way

This is a very common Icelandic expression. You will often see:

• á leiðinni heim = on the way home
• á leiðinni í skólann = on the way to school
• á leiðinni í vinnu = on the way to work

So in this sentence, á leiðinni functions almost like a set phrase.

Because á here means on in a location/state sense, and in that use it takes the dative.

Compare the idea:

• being on the way = location/state → dative

So:

• leiðinni is the dative singular definite form of leið
• á leiðinni = on the way

This fits a broader Icelandic pattern:

• á borðinu = on the table
• á gólfinu = on the floor
• á leiðinni = on the way

Í vinnu is a very common idiomatic expression meaning to work or to one’s job/workplace.

Even though English often uses to work, Icelandic frequently uses:

• í vinnu = to work / at work, depending on context

In many everyday expressions, Icelandic leaves out the definite article where English might use it. So:

• á leiðinni í vinnu = on the way to work

Using í vinnuna would sound more specifically like into the job / into the workplace in a more concrete or marked way. In ordinary everyday speech, í vinnu is the normal expression.

Syntactically, it is best understood as accusative, because í usually takes:

• accusative when there is movement into
• dative when there is location in

Here the idea is:

• á leiðinni í vinnu = on the way into/to work

So this is a motion/direction idea, which points to the accusative.

However, the form vinnu does not help you see the difference, because for the noun vinna, the accusative singular and dative singular are the same in form.

So the grammar says one thing, but the visible ending does not show the contrast.

Because á fimmtudögum means on Thursdays in the habitual sense.

The singular would mean a specific Thursday:

• á fimmtudag = on Thursday / on a Thursday

The plural means something repeated:

• á fimmtudögum = on Thursdays

That matches oft nicely, because the sentence is describing a repeated habit.

Because the preposition á is used for days of the week in this expression, and here it takes the dative.

So:

• fimmtudagur = Thursday
• fimmtudögum = Thursdays (dative plural)

This is a common time expression pattern:

• á mánudögum = on Mondays
• á þriðjudögum = on Tuesdays
• á fimmtudögum = on Thursdays

It is worth learning as a chunk.

It tells you when / in what situation the walking past happens: on the way to work.

The sentence breaks down roughly like this:

• Ég geng = I walk
• oft = often
• framhjá kirkjunni = past the church
• á leiðinni í vinnu = on the way to work
• á fimmtudögum = on Thursdays

So the church-passing happens specifically during the trip to work, not just at any time.

Yes, Icelandic word order is somewhat flexible, but the original sentence is very natural.

Original:

• Ég geng oft framhjá kirkjunni á leiðinni í vinnu á fimmtudögum.

You could also move parts around for emphasis, for example:

• Á fimmtudögum geng ég oft framhjá kirkjunni á leiðinni í vinnu.

That still means essentially the same thing, but now á fimmtudögum is emphasized more strongly.

A useful thing to remember is that Icelandic often moves elements for focus, but the verb still follows important word-order rules in main clauses.

Because Icelandic, like English, often uses short prepositional phrases to build up information step by step.

Here you get:

• framhjá kirkjunni = place/path
• á leiðinni = situation/state
• í vinnu = destination
• á fimmtudögum = time

So the sentence is compact, but each phrase adds one more detail:

1. what you do
2. where you pass
3. during what journey
4. to where
5. on which days

This kind of stacking is very common in real Icelandic.