Ég klippi pappírinn áður en ég festi hann með límbandi.

The ending -inn is the definite article in Icelandic, attached to the noun itself.

• pappír = paper
• pappírinn = the paper

Unlike English, Icelandic usually adds the onto the end of the noun instead of writing it as a separate word.

Because klippa is the infinitive form, meaning to cut, while klippi is the form used with ég (I) in the present tense.

So:

• að klippa = to cut
• ég klippi = I cut / I am cutting

This is a very common pattern in Icelandic verbs:

• að festa → ég festi
• að tala → ég tala

Some verbs change more than others, but here klippa → klippi is just the normal 1st person singular present form.

Áður en means before in the sense of before something happens / before I do something.

In this sentence:

• Ég klippi pappírinn áður en ég festi hann með límbandi.
• I cut the paper before I attach it with tape.

A useful way to think of it is:

• áður = earlier / before
• en = part of the conjunction here, introducing the clause

So áður en ég festi hann... means before I attach it...

Because Icelandic, like English, normally repeats the subject in a new clause.

The sentence has two clauses:

1. Ég klippi pappírinn
2. áður en ég festi hann með límbandi

In English we also say:

• I cut the paper before I attach it with tape

We do not usually say before attach it. Icelandic works the same way here: the second clause needs its own subject, ég.

Yes, hann can mean he, but it can also mean it when referring to a masculine noun.

In Icelandic, every noun has a grammatical gender:

• masculine
• feminine
• neuter

Pappír is a masculine noun, so when you refer back to it, you use hann.

So here:

• pappírinn = the paper
• hann = it (referring to the paper)

This is grammatical gender, not biological sex.

Because hann is the object of festi.

In the clause:

• ég festi hann með límbandi

the verb festa means attach / fasten, and hann is the thing being attached, so it is the direct object.

For a masculine singular pronoun, the accusative form is:

• hann

So this is the correct object form here.

After the preposition með, Icelandic often uses the dative case when it means with in the sense of using something.

Here:

• með límbandi = with tape

The noun is:

• límband = tape
• dative singular: límbandi

So með límbandi literally means something like with tape / using tape.

This is a very important Icelandic pattern: prepositions often control a specific case.

The base form is að festa, which means to fasten, attach, fix.

In this sentence:

• ég festi = I attach / I fasten

So the pattern is:

• að festa = infinitive
• ég festi = present tense, I attach

This is parallel to:

• að klippa → ég klippi

Icelandic often uses the present tense in general statements, habitual actions, instructions, or descriptions of a sequence of actions.

So this sentence can mean something like:

• I cut the paper before I attach it with tape
• I cut the paper before attaching it with tape
• I cut the paper first, then tape it

Even though the actions happen in sequence, Icelandic does not need a special tense here. English also often does the same:

• I wash the vegetables before I cook them.

So the present tense is completely natural.

The basic word order is quite straightforward:

• Ég klippi pappírinn
  I cut the paper
• áður en ég festi hann með límbandi
  before I attach it with tape

So the order is basically:

Subject + Verb + Object

and then

Subordinating expression + Subject + Verb + Object + Prepositional phrase

Nothing especially unusual is happening here, which makes this a good beginner-friendly sentence.

Yes. Icelandic present tense often covers both:

• I cut
• I am cutting

So:

• Ég klippi pappírinn could mean I cut the paper or I am cutting the paper, depending on context.

In this full sentence, the most natural interpretation is usually a general or sequential one:

• I cut the paper before I attach it with tape

But context always decides the best English translation.

Límband specifically means adhesive tape.

It is made from:

• lím = glue
• band = strip / ribbon / band

So límband is literally something like glue-strip, which matches the idea of tape quite well.

In this sentence, með límbandi clearly means with tape in the ordinary adhesive sense.

In this sentence, hann most naturally refers to pappírinn because that is the object just mentioned, and it makes sense semantically:

• I cut the paper before I attach it with tape

That is the logical interpretation.

Also, the gender matches:

• pappírinn is masculine
• hann is the masculine pronoun used for it

So grammar and meaning both point to hann = the paper.