Мне не нравится такой фильм, потому что он слишком скучный.

Because the verb нравиться works differently from English to like.

In English, we say I like the film.
In Russian, the structure is closer to The film is pleasing to me.

So:

• мне = to me (dative case)
• нравится = is pleasing / is liked
• фильм is the thing being liked

So Мне не нравится такой фильм literally feels like:

To me, such a film is not pleasing.

That is why я is not used here.

The verb нравиться agrees with the thing that is pleasing, not with the person in мне.

Here the thing being liked is такой фильм — one film, masculine singular.
So the verb is singular:

• фильм нравится = the film is pleasing

Compare:

• Мне нравится фильм. = I like the film.
• Мне нравятся фильмы. = I like films.

So нравится is singular because фильм is singular.

Both are possible, but they are not exactly the same.

• Мне не нравится такой фильм = I don’t like this kind of film / This kind of film doesn’t appeal to me.
• Я не люблю такие фильмы = I don’t like such films / I don’t enjoy such films in general.

Нравиться is often used for opinions, reactions, and preferences.
Любить is stronger and can sound more general or deeper.

So in this sentence, не нравится is natural because it expresses a personal reaction to the film type.

Такой means such, this kind of, or like that, depending on context.

In такой фильм, it means:

• such a film
• this kind of film

So the speaker is not only talking about one specific movie, but about a film of that type.

Compare:

• этот фильм = this film (a specific one)
• такой фильм = this kind of film / such a film

Because такой must match the noun it describes in case, gender, and number.

Here фильм is:

• masculine
• singular
• nominative case

So the adjective must also be masculine singular nominative:

• такой фильм

You would get такого фильма only if the noun were in the genitive case.

For example:

• У меня нет такого фильма. = I don’t have such a film.

But in your sentence, фильм is the subject-like element of нравится, so nominative is used.

Он refers back to фильм.

Since фильм is a masculine noun, the pronoun is masculine too:

• фильм → он

So:

• потому что он слишком скучный = because it/he is too boring

In English we say it for things, but in Russian nouns have grammatical gender, so a masculine noun is replaced by он.

Other examples:

• книга → она
• окно → оно

Слишком means too, not just very.

So:

• слишком скучный = too boring

If you wanted very boring, you would more naturally say:

• очень скучный = very boring

This is an important difference:

• очень = very
• слишком = too, excessively

So the sentence suggests the boredom is excessive enough to be a problem.

Because скучный is an adjective describing the noun фильм.

• фильм скучный = the film is boring

Here он stands for фильм, so the adjective must agree with it:

• masculine singular → скучный

By contrast, скучно is usually an adverb or a predicative word:

• Мне скучно. = I am bored.
• Здесь скучно. = It is boring here.

So:

• фильм скучный = the film is boring
• мне скучно = I am bored

Those are different structures.

In the present tense, Russian usually omits to be.

So:

• Он скучный. literally = He/it boring
• natural English = He/it is boring

This is completely normal in Russian.

Compare:

• Она дома. = She is at home.
• Я студент. = I am a student.
• Фильм скучный. = The film is boring.

In past and future, forms of быть do appear:

• Фильм был скучный. = The film was boring.
• Фильм будет скучный. = The film will be boring.

Yes, Russian word order is flexible.

The given order is natural and neutral:

• Мне не нравится такой фильм.

But you could also say:

• Такой фильм мне не нравится.
• Мне такой фильм не нравится.

These versions change emphasis slightly:

• Такой фильм мне не нравится puts more focus on that kind of film
• Мне такой фильм не нравится can emphasize to me

Russian uses word order more for emphasis and information flow than English does.

Потому что means because.

It introduces the reason:

• Мне не нравится такой фильм = I don’t like this kind of film
• потому что он слишком скучный = because it is too boring

So the second clause explains the first.

You may also see так как for since / because, but потому что is the most direct and common choice in everyday speech.

You can, but it would sound a bit less natural in many contexts.

For one film or this kind of film, Russian often prefers мне не нравится.

More natural alternatives:

• Мне не нравится такой фильм.
• Я не люблю такие фильмы. = I don’t like films like that.

Why?

• такой фильм sounds like such a film / this kind of film
• не люблю often works better with a broader generalization, so plural такие фильмы is often more idiomatic

So your original sentence is a very good, natural choice.

Russian does not have articles.

English distinguishes:

• a film
• the film

Russian simply says фильм, and the exact meaning comes from context.

In your sentence:

• такой фильм already gives the sense of such a film / this kind of film

So no extra word is needed.

Usually it suggests a type or kind, not just one specific title.

So Мне не нравится такой фильм most naturally means:

• I don’t like this kind of film.
• I don’t like a film like this.

If you wanted to point to one specific movie, you would more likely say:

• Мне не нравится этот фильм. = I don’t like this film.

So такой is broader and more descriptive than этот.

Normally, yes. The standard negation is:

• не нравится = do/does not like

So:

• Мне не нравится фильм.

Russian usually places не directly before the word it negates. Here it negates the verb нравится.

You may see different word orders in the sentence as a whole, but не нравится usually stays together.

For example:

• Мне не нравится такой фильм.
• Такой фильм мне не нравится.

Both are fine.