A feladó, aki nyomon követi a küldeményt, ma reklamál.

The basic skeleton is:

• A feladó = the sender → the subject
• aki nyomon követi a küldeményt = who tracks / is tracking the shipment → a relative clause describing the sender
• ma = today
• reklamál = complains / makes a complaint

So the full structure is:

The sender, who is tracking the shipment, is complaining today.

The relative clause in the middle simply adds extra information about the sender.

A is the Hungarian definite article, meaning the.

• a feladó = the sender
• egy feladó = a sender

Here it is definite because the sentence is talking about a specific sender, not just any sender.

Aki means who, and it is used for people.

Since feladó refers to a person, Hungarian uses aki:

• a feladó, aki... = the sender, who...

If the noun were not a person, Hungarian would usually use amely or sometimes ami, depending on the context.

That part is a non-restrictive relative clause: it adds extra information rather than identifying which sender we mean.

So Hungarian, like English, puts commas around it:

• A feladó, aki nyomon követi a küldeményt, ma reklamál.

This is similar to English:

• The sender, who is tracking the shipment, is complaining today.

If the relative clause were essential to identifying the person, the punctuation could work differently in English, but in Hungarian this kind of inserted descriptive clause is normally set off with commas.

Nyomon követ is a fixed expression meaning to track, to follow the progress of, or literally something like to follow along the trace.

Breakdown:

• nyom = trace, mark
• nyomon = roughly along the trace / on the trail
• követ = follow

Together, nyomon követ functions like one verbal expression:

• nyomon követi a küldeményt = he/she tracks the shipment

So you should learn nyomon követ as a unit, not as two separate random words.

Because Hungarian verbs can use two different conjugation patterns:

• indefinite conjugation
• definite conjugation

Here the object is definite:

• a küldeményt = the shipment

So Hungarian uses the definite form of the verb:

• követi = tracks it / tracks the ...

Compare:

• követ egy küldeményt = tracks a shipment → indefinite object, so követ
• követi a küldeményt = tracks the shipment → definite object, so követi

This is a very important feature of Hungarian grammar.

The -t ending marks the accusative case, which is used for the direct object.

• küldemény = shipment (dictionary form)
• küldeményt = shipment as the thing being acted on

Since the sender is tracking the shipment, küldemény is the direct object of követi, so it gets -t.

The change is:

• küldemény + t
• with linking/pronunciation adjustment: küldeményt

So:

• követi a küldeményt = tracks the shipment

It can mean either, depending on context.

Hungarian does not usually make the same strict distinction between:

• tracks
• is tracking

with a special verb form the way English does.

So követi can mean:

• tracks
• is tracking
• has been tracking, in the right context

Likewise:

• reklamál can mean complains, is complaining, or makes a complaint

The exact English translation depends on the situation.

Reklamál means to complain, especially in the sense of making a complaint about a product, service, delivery, or problem.

In this sentence, it most naturally means something like:

• is making a complaint
• complains
• files a complaint

So this is not just general grumbling; it often has a practical, customer-service flavor.

In Hungarian, adverbs of time often appear before the verb, especially in a neutral sentence.

So:

• ma reklamál = complains today / is complaining today

This placement is very natural.

Word order can change, but that usually changes emphasis:

• A feladó ... ma reklamál. → neutral, natural
• Ma reklamál a feladó. → stronger emphasis on today
• A feladó ... reklamál ma. → possible, but less neutral in ordinary prose

So the sentence as given has a normal, natural word order.

Yes. Feladó comes from the verb felad, which can mean to send, to post, or in other contexts to give up.

In the postal/shipping context:

• felad egy csomagot = send / post a package
• feladó = sender

So feladó is the person who sent the shipment.

Because it agrees with a feladó, which is singular:

• a feladó = the sender → one person

So the relative clause also refers to that one person:

• aki ... követi ... = who ... tracks ...

If the subject were plural, the verb would change:

• A feladók, akik nyomon követik a küldeményt, ma reklamálnak.
• The senders, who are tracking the shipment, are complaining today.

So követi matches the singular subject feladó.