Ég hélt að umræðuefnið væri einfalt, en fundargerðin sýndi að við skildum það ekki öll á sama hátt.

Here hélt is the past tense of halda, but with an að-clause it often means think, believe, or assume.

So:

• Ég hélt á bókinni = I held the book
• Ég hélt að... = I thought that...

In this sentence, Ég hélt að umræðuefnið væri einfalt means I thought the topic was simple.

Væri is the past subjunctive of vera (to be).

It is very common after verbs like halda when the speaker is reporting a belief, assumption, or impression rather than stating a solid fact. It often suggests some distance: this was what the speaker believed at the time, but it may not actually have been true.

That fits this sentence well, because the second half shows that the situation was more complicated than the speaker first thought.

So væri here gives the sense of:

• I thought it was simple
• but that turned out not to be the full story

Umræðuefnið is a compound noun.

It is built from:

• umræða = discussion
• efni = subject, material, topic

Together, umræðuefni means topic of discussion or discussion topic.

Then -ið is the suffixed definite article, so:

• umræðuefni = a discussion topic
• umræðuefnið = the discussion topic / the topic under discussion

Because the head noun is efni, which is neuter singular, the whole compound is treated as neuter singular.

Because it agrees with umræðuefnið, which is neuter singular.

The adjective is based on einfaldur = simple, and its neuter singular form is einfalt.

So:

• masculine: einfaldur
• feminine: einföld
• neuter: einfalt

Since umræðuefnið is neuter singular, Icelandic uses einfalt.

Fundargerð means minutes of a meeting, meeting record, or written record of the meeting.

English usually uses a plural expression, the minutes, but Icelandic often uses the singular noun fundargerð.

Then -in is the suffixed definite article:

• fundargerð = meeting minutes / a meeting record
• fundargerðin = the meeting minutes / the meeting record

It is a feminine noun, which is why the definite form looks like -in here.

Sýndi is the past tense of sýna, which means to show.

Here it means something like showed, revealed, or made clear.

Since the subject is fundargerðin, which is singular, the verb is singular too:

• fundargerðin sýndi = the minutes showed

Skildum is the 1st person plural past tense of skilja = to understand.

So:

• við skiljum = we understand
• við skildum = we understood

In this sentence:

• við skildum það ekki = we did not understand it

Both instances of að introduce subordinate clauses, just like English that.

• Ég hélt að... = I thought that...
• fundargerðin sýndi að... = the minutes showed that...

So the sentence has two main clauses, and each one contains its own that-clause.

Það means it, and it refers back to umræðuefnið.

Because umræðuefnið is neuter singular, the pronoun referring to it is also neuter singular:

• umræðuefnið = neuter singular
• það = it for a neuter singular noun

So við skildum það ekki... means we did not understand it...

Öll is the neuter plural form of allur = all.

When við refers to a mixed group or a group whose gender is not being specified, Icelandic often uses the neuter plural form. So:

• við öll = we all / all of us

If the group were specifically all male, you might see allir. If specifically all female, allar.

So öll here is the normal inclusive form for all of us.

Word for word, it is roughly:

• við = we
• skildum = understood
• það = it
• ekki = not
• öll = all

So literally: we understood it not all

Natural English would be:

• we did not all understand it
• or not all of us understood it

That is slightly different from we all did not understand it, which can sound more absolute in English. The Icelandic phrasing emphasizes that understanding was not shared equally across the whole group.

That word order is very normal in Icelandic.

Short object pronouns such as það often come before ekki, so:

• við skildum það ekki

is a natural way to say we did not understand it.

English learners often expect ekki to come immediately after the verb every time, but Icelandic word order is more flexible, and pronouns frequently appear before the negation.

It means in the same way.

The phrase is:

• á = on, in, at
• sama = same
• hátt = way, manner

Together, á sama hátt is an idiomatic expression meaning in the same way or in the same manner.

It is best learned as a whole phrase.

Yes, completely normal.

The sentence has two main clauses joined by en = but:

• Ég hélt að umræðuefnið væri einfalt
• en fundargerðin sýndi að við skildum það ekki öll á sama hátt

Each main clause contains a subordinate að-clause. This is a very common way to build longer Icelandic sentences.

So structurally, it is a good example of standard written Icelandic:

• main clause
• embedded that-clause
• contrast with en
• another main clause
• another embedded that-clause