Tescil belgesi koruma süresini gösteriyor.

The sentence uses the very common Turkish pattern subject + object + verb.

• Tescil belgesi = subject
• koruma süresini = direct object
• gösteriyor = verb

So the literal order is something like:

• Registration certificate protection period shows

That sounds odd in English, but it is normal in Turkish because the verb usually comes at the end.

Because tescil belgesi is a noun compound.

• tescil = registration
• belge = document / certificate

In Turkish, compounds like registration certificate are often formed by putting two nouns together, and the second noun usually takes a special ending: -(s)ı / -(s)i / -(s)u / -(s)ü.

So:

• belge → belgesi
• tescil belgesi = registration certificate / registration document

This does not necessarily mean literal possession. It is just the normal way Turkish forms many compound nouns.

There are two things happening here.

First, koruma süresi is itself a noun compound:

• koruma = protection
• süre = duration / period
• koruma süresi = protection period

So süre becomes süresi because it is the second noun in the compound.

Second, that whole phrase is the direct object of the verb gösteriyor, and it is a specific object, so it takes the accusative ending.

So:

• koruma süresi = protection period
• koruma süresini = the protection period (as a direct object)

It is the accusative case ending used for a specific/definite direct object.

Breakdown:

• süre = period
• süresi = its period / period of X / period in a compound
• süresini = that period, as the direct object

The n is a buffer consonant. After certain possessive endings, Turkish uses n before another suffix.

So here:

• süresi
  • accusative → süresini

Because subjects in Turkish are usually in the unmarked nominative form, while direct objects are often marked if they are specific.

So here:

• Tescil belgesi = subject, no special ending
• koruma süresini = specific direct object, so it takes accusative

This is very common in Turkish:

• subject: often unmarked
• definite/specific object: marked with accusative

Gösteriyor is from the verb göstermek = to show.

It contains the Turkish present continuous/progressive marker:

• göster- = show
• -iyor = is doing / doing

So gösteriyor literally means something like:

• is showing

But in Turkish, this form is also very often used where English would simply say:

• shows
• indicates

So in this sentence, gösteriyor can naturally correspond to English shows.

Both are possible, but they feel a little different.

• gösteriyor often sounds like a current, direct description:
  The certificate shows the protection period.
• gösterir can sound more general, formal, or rule-like:
  The certificate indicates the protection period.

In modern everyday Turkish, -iyor is extremely common, even where English might use the simple present.

Turkish does not use articles the same way English does.

There is no exact equivalent of the in ordinary Turkish grammar, and a/an is often expressed with bir when needed.

So Turkish relies on:

• context
• word order
• case endings
• other determiners

In this sentence, the accusative in koruma süresini helps give the sense of a specific protection period.

Yes. Turkish word order is flexible, although subject + object + verb is the neutral pattern here.

For example, you could move things around for emphasis:

• Koruma süresini tescil belgesi gösteriyor.

This still means basically the same thing, but now the object koruma süresini is more prominent.

So Turkish word order is not random, but it is more flexible than English.

Because Turkish usually does not need a subject pronoun when the subject is already stated or understood.

Here the subject is explicitly given:

• Tescil belgesi

So there is no need to add o (it/he/she).

Also, the verb form already tells you the person:

• gösteriyor = it/he/she is showing or shows

Since tescil belgesi is already there, the sentence is complete without any pronoun.

Here they function as nouns.

• tescil = registration
• koruma = protection

Turkish often uses noun-like forms to build compounds such as:

• tescil belgesi = registration certificate
• koruma süresi = protection period

So instead of using a structure like English the period of protection, Turkish often just puts the words together in a compound form.

The dictionary form is göstermek, meaning to show.

You can think of the sentence verb as:

• göstermek = to show
• gösteriyor = is showing / shows

When learning Turkish, it is useful to identify the dictionary form of verbs, because suffixes are then added onto that base in predictable ways.