Pratim vijesti na mreži svake večeri.

Because Croatian usually leaves out subject pronouns when they are obvious from the verb form.

Pratim already means I follow / I keep up with, so ja is not necessary.

You could say Ja pratim vijesti na mreži svake večeri, but that would sound more emphatic, like:

• I follow the news every evening.
• As for me, I follow the news every evening.

The neutral version is the one without ja.

Pratim is the 1st person singular present tense form of the verb pratiti.

So:

• pratiti = to follow
• pratim = I follow / I am following

In this sentence, it means something like I follow / keep up with the news.

This is an imperfective verb, which fits a repeated or ongoing habit such as every evening.

In Croatian, vijest means a piece of news / an item of news, and vijesti is the plural form, meaning news in the general sense.

So Croatian treats news as grammatically plural much more often than English does.

• vijest = one news item
• vijesti = news

That is why Pratim vijesti is the normal way to say I follow the news.

Here, vijesti is in the accusative plural, because it is the direct object of pratim.

You are following what? → vijesti

For this noun, the accusative plural looks the same as the nominative plural:

• nominative plural: vijesti
• accusative plural: vijesti

So the form does not change, but its function in the sentence is accusative.

Yes, but the meaning is slightly different.

• pratiti vijesti = to follow the news, to keep up with current events
• gledati vijesti = to watch the news

So pratim vijesti is broader. It can include reading news online, watching it, listening to it, or just keeping up with it in general.

Because the sentence also says na mreži, pratim vijesti works very naturally here.

Literally, na mreži means on the network, but in normal usage it means online or on the web.

Here, na is followed by the locative case because it expresses location, not motion.

• mreža = network
• locative singular: mreži

So:

• na mreži = on the network / online

This is a normal Croatian way to express the idea of being online.

Yes. Na internetu is also very common and may sound even more natural to many learners because it is more transparent.

So these are both possible:

• Pratim vijesti na mreži.
• Pratim vijesti na internetu.

You may also hear online in everyday speech.

The nuance is roughly:

• na mreži = online, on the web
• na internetu = on the internet

In many contexts, they are very close in meaning.

Svake večeri is a standard Croatian way to say every evening.

This uses the genitive singular:

• svake = genitive singular feminine of svaki
• večeri = genitive singular of večer

Croatian often uses the genitive in expressions of repeated time:

• svakog dana = every day
• svake noći = every night
• svake večeri = every evening

So this is not a word-for-word match with English grammar; it is just the normal Croatian pattern.

Yes, you may hear svaku večer as well, and it is widely understood and used.

However, svake večeri is a very common and standard way to express repeated time, especially in grammar explanations.

So for a learner:

• svake večeri = a very solid standard choice
• svaku večer = also common in real usage

If you want the safest version for study, keep svake večeri.

Croatian word order is fairly flexible, because case endings show the grammatical roles.

So these are all possible, with slightly different emphasis:

• Pratim vijesti na mreži svake večeri.
• Svake večeri pratim vijesti na mreži.
• Na mreži pratim vijesti svake večeri.

The original sentence sounds natural and neutral. If you move svake večeri to the front, you give more emphasis to the time:

• Svake večeri pratim vijesti na mreži. = Every evening, I follow the news online.

Yes:

• Pratim — 1st person singular, present tense of pratiti; I follow
• vijesti — accusative plural of vijest; news
• na — preposition; here it means on
• mreži — locative singular of mreža; network, so na mreži = online
• svake — genitive singular feminine of svaki; every
• večeri — genitive singular of večer; evening

So the structure is basically:

[verb] + [direct object] + [place expression] + [time expression]