Otkad mi je sestra pokazala kako priložiti datoteku, više ne šaljem prazne poruke.

Otkad means since when / ever since. In this sentence, it introduces the point in time after which the situation changed:

Otkad mi je sestra pokazala kako priložiti datoteku...
= Ever since my sister showed me how to attach a file...

A useful distinction:

• kad = when
• otkad = since / ever since
• dokad = until when

So otkad marks the starting point of a continuing situation.

The comma separates the subordinate clause from the main clause.

• Otkad mi je sestra pokazala kako priložiti datoteku = subordinate time clause
• više ne šaljem prazne poruke = main clause

Croatian normally uses a comma before or after subordinate clauses like this, especially when the dependent clause comes first.

Mi means to me.

So:

• sestra je pokazala = my sister showed
• sestra mi je pokazala = my sister showed me

This is the dative case of ja:

• ja = I
• meni / mi = to me

Here mi is the short unstressed form, which is very common in normal speech and writing.

All of these are possible, but they are not equally neutral.

Mi je sestra pokazala is a very natural Croatian word order because short unstressed words like mi and je tend to come very early in the sentence, in the so-called second position.

About sestra vs moja sestra:

• sestra can already mean my sister from context
• Croatian often omits possessives like my, your, his, when they are obvious

So mi je sestra pokazala naturally means my sister showed me.

If you said moja sestra mi je pokazala, that is also correct, but slightly more explicit or emphatic.

Because je is a clitic, a short unstressed form that usually appears near the beginning of the clause.

In Croatian, clitics such as:

• je
• sam
• si
• mi
• ti
• ga
• se

tend to cluster in second position.

So instead of a more English-like order such as sestra je mi pokazala (which is wrong), Croatian prefers:

• mi je sestra pokazala

This is one of the most important Croatian word-order habits for learners to get used to.

Because sestra is feminine singular, and the Croatian past tense agrees with the subject in gender and number.

• pokazao = masculine singular
• pokazala = feminine singular
• pokazalo = neuter singular
• pokazali / pokazale = plural

Since sestra is feminine singular, the correct form is pokazala.

The full past tense here is:

• je pokazala = showed / has shown

Because the sentence describes a past event that caused a present, ongoing result.

• mi je sestra pokazala = one completed event in the past
• više ne šaljem = what I do now, as a general current habit

So the logic is:

Since my sister showed me how to attach a file, I no longer send empty messages.

Croatian often uses the present tense for current habits or general truths, just like English does here.

Literally, it means how to attach a file.

This pattern is very common in Croatian:

• kako + infinitive

Examples:

• kako otvoriti dokument = how to open a document
• kako poslati poruku = how to send a message
• kako priložiti datoteku = how to attach a file

English can also do this with how to..., so this part maps quite neatly between the two languages.

Priložiti is the perfective verb, meaning a single completed act: to attach.

Croatian often uses the perfective infinitive in instructions about accomplishing one action:

• kako priložiti datoteku = how to attach a file

The imperfective partner would be something like prilagati, but that would sound less natural here because the sentence is about learning how to perform the action successfully, not about an ongoing repeated process.

For learners, the simplest takeaway is:

• priložiti = to attach, as a completed action
• good choice in instructional phrases like how to attach...

Because datoteku is in the accusative singular, the case used for a direct object.

Base form:

• datoteka = file

Accusative singular:

• datoteku

So:

• priložiti datoteku = to attach a file

This happens because datoteka is a feminine noun ending in -a, and many such nouns change:

• nominative: datoteka
• accusative: datoteku

Yes, više often means more, but in the expression više ne, it means no longer / not anymore.

So:

• više ne šaljem = I no longer send
• literally something like I send no more

This is a very common Croatian pattern:

• više ne radim tamo = I no longer work there
• više ne pušim = I don’t smoke anymore
• više ne šaljem prazne poruke = I no longer send empty messages

So learners should memorize više ne as a set phrase.

Šaljem is the 1st person singular present tense of slati / slati slati? More standardly, the verb is slati = to send, and šaljem is its present-tense form meaning I send.

Examples:

• šaljem = I send
• šalješ = you send
• šalje = he/she/it sends

Here:

• više ne šaljem prazne poruke = I no longer send empty messages

Even though the form is present tense, it describes a current habitual fact.

Because prazne poruke is the accusative plural, used as the direct object of šaljem.

Base forms:

• prazna poruka = empty message

Plural nominative:

• prazne poruke = empty messages

For feminine plural nouns like poruke, the accusative plural is the same as the nominative plural:

• poruke = messages
• prazne poruke = empty messages

So:

• šaljem prazne poruke = I send empty messages

By contrast, praznih poruka would be genitive plural, which is not what the verb needs here.

Yes to both.

• datoteka = the standard Croatian word for file
• fajl = a common informal borrowing from English file

In more standard or careful Croatian, especially in manuals, school, or official contexts, datoteka is preferred. In everyday speech, many people also use fajl.

So priložiti datoteku is perfectly natural and standard.

Yes, to some extent. Croatian word order is more flexible than English word order, but not random.

For example, these can all be possible depending on emphasis:

• Otkad mi je sestra pokazala kako priložiti datoteku, više ne šaljem prazne poruke.
• Više ne šaljem prazne poruke otkad mi je sestra pokazala kako priložiti datoteku.

But you must still respect clitic placement. That is why forms like je, mi, se, etc. cannot just be dropped anywhere.

The original sentence sounds very natural and neutral.

Yes, they mean the same thing.

• otkad
• od kada

Both mean since when / ever since.

Otkad is the more compact one-word form and is very common. Od kada is also correct and may feel a bit more explicit. In this sentence, otkad is completely natural.

A useful way to break it down is:

• Otkad = since
• mi je sestra pokazala = my sister showed me
• kako priložiti datoteku = how to attach a file
• više ne šaljem = I no longer send
• prazne poruke = empty messages

So the structure is:

Since + past event, present result.

This is a very common Croatian pattern, and it works much like English:

Ever since X happened, Y is now true.