Ja više ne radim tamo.

Yes, ja can be omitted.

Serbian often leaves out subject pronouns because the verb ending already shows who is doing the action.

• radim = I work / I am working

So:

• Ja više ne radim tamo.
• Više ne radim tamo.

both mean the same thing.

Including ja usually adds a bit of emphasis, contrast, or clarity, as if saying:

• I don’t work there anymore.

Više ne means no longer, not anymore, or not ... anymore.

In this sentence:

• više ne radim = I no longer work / I don’t work anymore

A very useful pattern is:

• više ne + verb

Examples:

• Više ne pušim. = I don’t smoke anymore.
• Više ne živimo ovde. = We don’t live here anymore.

Be careful: više on its own often means more, but in the pattern više ne, it means anymore / no longer.

In Serbian, the negative particle ne normally goes directly before the finite verb.

So:

• radim = I work
• ne radim = I do not work

In your sentence, više comes before that whole negative verb phrase:

• više ne radim

So the structure is:

• Ja = I
• više = anymore / no longer
• ne radim = do not work
• tamo = there

Radim is the 1st person singular present tense of the verb raditi.

That means:

• raditi = to work
• radim = I work / I am working

A few present-tense forms of raditi:

• ja radim = I work
• ti radiš = you work
• on/ona/ono radi = he/she/it works
• mi radimo = we work
• vi radite = you work
• oni/one/ona rade = they work

It can mean both, depending on context.

Serbian does not usually separate I work and I am working the way English does. The present tense often covers both ideas.

So radim can mean:

• I work
• I am working

In this sentence, because of više ne, the natural meaning is:

• I don’t work there anymore or
• I no longer work there

Yes, Serbian word order is fairly flexible, but different orders can sound more neutral, more emphatic, or more focused.

The most natural neutral version is:

• Ja više ne radim tamo.

You may also hear:

• Više ne radim tamo.
• Ja tamo više ne radim.
• Tamo više ne radim.

These all basically mean the same thing, but the focus shifts a little:

• tamo earlier in the sentence can emphasize there
• ja can emphasize I
• više ne usually stays together because it functions as a set phrase meaning no longer

Tamo means there.

Serbian has several location words:

• ovde = here
• tu = there / here near you / at that spot
• tamo = there, over there, in that place

In everyday speech, the exact distinction is not always strict, but generally:

• ovde = near the speaker
• tu = near the listener or at a specific nearby place
• tamo = farther away / that place over there

So Ja više ne radim tamo means:

• I don’t work there anymore.

Because it describes a current fact about your situation now.

The idea is not I worked there in the past.
The idea is:

• Now, it is true that I do not work there anymore.

So the present tense is exactly what Serbian needs here.

Compare:

• Radio sam tamo. = I worked there.
• Više ne radim tamo. = I don’t work there anymore.

The first talks about a past action/state.
The second talks about your present reality.

Not in this sentence.

By itself, više often means more:

• više novca = more money
• više radim = I work more

But when you see više ne, it is usually understood as:

• no longer
• not anymore

So in Ja više ne radim tamo, više does not mean more.

Yes.

If everyone already knows which workplace is being discussed, you can simply say:

• Više ne radim.

That means:

• I’m not working anymore or
• I don’t work anymore

But adding tamo makes it specific:

• Više ne radim tamo. = I don’t work there anymore.

Both can be understood, but Ja više ne radim tamo is the more standard and natural way to express I don’t work there anymore.

Why? Because više ne is a very common fixed pattern for no longer / not anymore.

• Ja više ne radim tamo. = very natural
• Ja ne radim tamo više. = possible, but less neutral and often sounds more marked or conversational

For learners, it is best to remember:

• više ne + verb

Yes. Raditi can also mean to do, to function, or to operate, depending on context.

Examples:

• Šta radiš? = What are you doing?
• Mašina radi. = The machine is working.
• On radi u školi. = He works at a school.

In your sentence, because of tamo and the overall context, radim is naturally understood as work there, not do there.