Považujeme tento film za dlouhý.

Považujeme is the 1st person plural present tense form of the verb považovat.

So it means we consider, we regard, or we think of ... as ....

Breakdown:

• považovat = to consider / to regard
• považujeme = we consider

This verb is often used in the pattern:

považovat něco / někoho za ...
= to consider something / someone ...

So in this sentence:

• Považujeme = We consider

Tento means this, so tento film = this film.

You could say just film if you meant a film or the film depending on context, but tento film specifically points to this particular film.

So:

• film = film / movie
• tento film = this film

A learner may also notice that tento changes form depending on case, gender, and number. Here it matches film, which is:

• masculine inanimate
• singular
• accusative

It is in the accusative case because it is the direct object of the verb považujeme.

We are considering what?

• tento film

That makes it the object.

So:

• Považujeme koho/co? → tento film

That is why accusative is used.

A useful extra point: with masculine inanimate nouns, the accusative singular is often the same as the nominative singular. So film stays film.

With považovat, Czech commonly uses the structure:

považovat něco / někoho za ...

This means:

• to consider something/someone to be ...
• to regard something/someone as ...

So za is part of the normal grammar pattern of this verb.

Examples:

• Považuji ho za přítele. = I consider him a friend.
• Považují tu knihu za důležitou. = They consider that book important.

In your sentence:

• Považujeme tento film za dlouhý. = We consider this film long.

So za is not being translated literally as for here. It is just part of the fixed construction.

Dlouhý is an adjective meaning long.

Here it describes how we consider the film. In other words, it is the quality assigned to tento film.

So the structure is:

• Považujeme = we consider
• tento film = this film
• za dlouhý = to be long / as long

The adjective agrees with film:

• masculine
• singular
• accusative

Because film is masculine inanimate singular, the accusative form of dlouhý looks the same as the nominative:

• nominative: dlouhý
• accusative masculine inanimate: dlouhý

Because dlouho is an adverb, while dlouhý is an adjective.

Here we need an adjective because it describes the noun film.

Compare:

• dlouhý film = a long film
• Film je dlouhý. = The film is long.
• Považujeme tento film za dlouhý. = We consider this film long.

But:

• dlouho = for a long time / long

Example with the adverb:

• Film trvá dlouho. = The film lasts a long time.

So:

• describing a noun → use dlouhý
• describing duration or manner → use dlouho

Because film is a masculine inanimate noun, and in the singular, masculine inanimate nouns usually have the same form in nominative and accusative.

So:

• nominative: film
• accusative: film

That is completely normal.

Compare that with a masculine animate noun, where the accusative usually changes:

• nominative: student
• accusative: studenta

So in your sentence, the case is accusative even though film looks unchanged.

Yes. Czech word order is more flexible than English word order.

The neutral version is:

Považujeme tento film za dlouhý.

But other orders are possible depending on emphasis, topic, or style, for example:

• Tento film považujeme za dlouhý.
• Za dlouhý považujeme tento film.

These alternatives can sound more marked or emphasize different parts of the sentence.

For a learner, the safest default is the original order:

• Považujeme tento film za dlouhý.

No, not by itself.

Dlouhý just means long.
So the sentence means We consider this film long or more naturally We think this film is long.

If you want too long, Czech would use příliš dlouhý:

• Považujeme tento film za příliš dlouhý.

So:

• dlouhý = long
• příliš dlouhý = too long

Yes, it is grammatical and natural.

That said, in everyday speech Czech speakers might also use other ways to express the same idea, such as:

• Myslíme si, že je ten film dlouhý. = We think the film is long.
• Ten film nám připadá dlouhý. = The film seems long to us.

But Považujeme tento film za dlouhý is perfectly correct and is a very useful pattern to learn because it shows the common construction:

považovat něco za + adjective/noun

Here are the dictionary forms:

• považujeme → považovat = to consider
• tento → dictionary form is already tento = this
• film → film = film / movie
• dlouhý → dlouhý = long

So if you were looking these up, those are the forms you would search for.