Daj mi škare; moram otvoriti paket i poslije vratiti ljepilo u ladicu.

Daj is the informal singular imperative of dati (to give), so it is used when speaking to one person informally.

• Daj mi škare. = Give me the scissors.
• Dajte mi škare. = Give me the scissors. (to one person formally, or to more than one person)

So this sentence sounds like the speaker is talking casually to one person.

Mi is the dative clitic form of ja (I / me), and here it means to me.

In Croatian, with dati (to give), the person receiving something is usually in the dative:

• Daj mi škare. = Give the scissors to me.

By contrast, mene is an accusative/genitive form, so it would not fit here.

Short version:

• mi = to me
• mene = me (as a direct object, in some contexts)

Škare means scissors and is normally used as a plural-only noun in Croatian, just like scissors in English.

So even though it refers to one object, the grammar is plural:

• škare su na stolu = the scissors are on the table
• daj mi škare = give me the scissors

A singular form is not normally used in everyday standard Croatian for the ordinary object. If you want to emphasize one pair of scissors, you can say:

• jedne škare = one pair of scissors

Here škare is the direct object, so it is in the accusative.

Because škare is an inanimate plural noun, the accusative has the same form as the nominative:

• nominative: škare
• accusative: škare

So in Daj mi škare, the form does not change, even though the case is accusative.

After modal verbs like morati (must / have to), Croatian normally uses the infinitive directly, without any extra word meaning to.

So:

• moram otvoriti = I have to open
• moram vratiti = I have to return / put back

This is very normal in Croatian:

• Moram ići. = I have to go.
• Moram raditi. = I have to work.

English uses to before the infinitive; Croatian does not.

This is about verb aspect.

• otvoriti = to open once, successfully, as a completed action
• vratiti = to return / put back as a completed action

In this sentence, the speaker means specific completed actions:

1. open the package
2. then put the glue back in the drawer

So the perfective verbs are natural here.

Compare:

• Moram otvoriti paket. = I need to open the package.
• Otvaram paket. = I am opening the package / I open packages.

And similarly:

• vratiti = put back once, complete the action
• vraćati = be returning / return repeatedly / habitually

Paket is in the accusative singular because it is the direct object of otvoriti.

• otvoriti paket = to open the package

Since paket is a masculine inanimate noun, its accusative singular is the same as its nominative singular:

• nominative: paket
• accusative: paket

If it were masculine animate, the accusative would usually look different.

Ljepilo is also a direct object, so it is in the accusative singular.

But ljepilo is a neuter noun, and for neuter nouns the accusative singular is the same as the nominative singular:

• nominative: ljepilo
• accusative: ljepilo

So:

• vratiti ljepilo = to put back the glue

This is a very important Croatian pattern:

• u + accusative = movement into somewhere
• u + locative = being in somewhere

Here the glue is being moved back into the drawer, so Croatian uses the accusative:

• vratiti ljepilo u ladicu = put the glue back into the drawer

Compare:

• Ljepilo je u ladici. = The glue is in the drawer.
  Here there is no movement, so it is locative.

So:

• u ladicu = into the drawer
• u ladici = in the drawer

Poslije here means afterwards / later / then after that.

In this sentence:

• moram otvoriti paket i poslije vratiti ljepilo u ladicu

it means the second action happens after the first one.

Croatian word order is fairly flexible, so poslije can often move around a bit:

• Moram otvoriti paket i poslije vratiti ljepilo u ladicu.
• Moram otvoriti paket i vratiti poslije ljepilo u ladicu.
• Poslije moram vratiti ljepilo u ladicu.

But the version in your sentence sounds natural and clear.

I means and. It links the two actions governed by moram:

• moram otvoriti paket
• (moram) vratiti ljepilo u ladicu

Croatian often avoids repeating the modal verb when it applies to both infinitives. So the full underlying idea is:

• Moram otvoriti paket i moram poslije vratiti ljepilo u ladicu.

Usually the second moram is omitted because it is understood.

Yes, often it could.

• poslije = afterwards / later
• onda = then

Both can work in similar contexts, though they are not always identical in tone.

For example:

• Moram otvoriti paket i poslije vratiti ljepilo u ladicu.
• Moram otvoriti paket i onda vratiti ljepilo u ladicu.

Both are natural.
Poslije slightly emphasizes after that / later, while onda often feels more like simple sequencing: then.

Croatian has special short pronoun forms called clitics, and mi is one of them. Clitics usually appear very early in the clause, typically in the second position.

So the natural order is:

• Daj mi škare.

not:

• Daj škare mi.

That second version sounds unnatural in standard Croatian.

This early placement of short pronouns is one of the most important word-order patterns for learners to notice.

The semicolon separates two closely connected parts:

1. Daj mi škare
2. moram otvoriti paket i poslije vratiti ljepilo u ladicu

It shows a stronger break than a comma, but a closer connection than a full stop.

In everyday writing, people might also write:

• Daj mi škare, moram otvoriti paket...
• Daj mi škare. Moram otvoriti paket...

So the semicolon is mainly a punctuation choice to connect two related ideas neatly.