Bu film büyük bir aşkı anlatıyor.

The basic order is Subject – Object – Verb, which is very common in Turkish.

• Bu film = the subject
• büyük bir aşkı = the direct object
• anlatıyor = the verb

So, literally, it is arranged like:

This film / a great love / tells

That is different from normal English word order, which is usually Subject – Verb – Object.

Bu means this.

So:

• bu film = this film

In Turkish, demonstratives like bu usually come before the noun, just like in English:

• bu kitap = this book
• bu ev = this house
• bu film = this film

In standard Turkish, when a noun has an adjective and also bir meaning a/an, the usual order is:

adjective + bir + noun

So:

• büyük bir aşk = a great love
• güzel bir ev = a beautiful house
• uzun bir yol = a long road

For an English speaker, bir büyük aşk may feel more natural because of English word order, but in normal Turkish the common pattern is büyük bir aşk.

Because aşkı is the direct object with the accusative ending.

The base noun is:

• aşk = love

Here it becomes:

• aşkı

That -ı is the accusative suffix. Turkish often marks a direct object when it is specific.

So:

• aşk = love
• aşkı = the love / a certain love / that love, as a direct object

The exact English translation depends on context, but the key grammar point is that -ı marks the noun as a specific object.

This is due to vowel harmony.

The accusative suffix has four forms:

• -ı
• -i
• -u
• -ü

Which one you use depends on the last vowel of the noun.

In aşk, the last vowel is a, so the correct accusative form is -ı:

• aşk → aşkı

A few more examples:

• ev → evi
• okul → okulu
• gül → gülü

This is a very common question.

In Turkish, bir does not automatically mean the object is non-specific in the way English a/an often does. Turkish distinguishes between:

• non-specific objects
• specific objects

So you can have:

• bir aşk = a love, some love, non-specific
• bir aşkı = a certain love, one particular love, specific

So büyük bir aşkı can mean something like a particular great love or one great love that the film is telling/depicting.

This is one place where Turkish does not match English article logic exactly.

Because film is the subject here, and subjects in Turkish are usually in the basic form with no special ending. This basic form is often called the nominative.

So:

• bu film = this film

There is no extra subject marker needed.

The object, however, can take case marking, which is why aşk becomes aşkı.

Anlatıyor comes from the verb anlatmak, which means to tell, to describe, to narrate, or sometimes to depict depending on context.

It breaks down like this:

• anlat- = verb stem
• -ıyor = present continuous / progressive marker

So:

• anlatıyor = is telling / tells / is describing

There is no extra ending for he/she/it here, because in the third person singular, Turkish often uses zero ending.

Because Turkish -iyor does not always match English is ...-ing exactly.

In Turkish, the present continuous is also often used for:

• what is happening now
• what something is doing in a general sense
• descriptions of books, films, and stories

So with a film, anlatıyor can naturally mean:

• is telling
• tells
• depicts
• portrays

In natural English, This film tells a great love story may sound better than This film is telling a great love story, even though Turkish uses -iyor.

Not separately. The subject is already stated as Bu film.

Turkish often does not use extra subject pronouns unless they are needed for emphasis. So once you have:

• Bu film = this film

there is no need to add a separate word for it.

Not always. Anlatmak has a wider range than English tell.

It can mean:

• to tell
• to explain
• to describe
• to narrate
• to depict

So with a person, it might mean explain or tell:

• Bana anlattı = He/She told me / explained to me

But with a film, book, or story, it often means:

• to tell
• to portray
• to be about

So in this sentence, anlatıyor is best understood in that broader sense.