Toto množství informací je důležité.

Toto is the neuter singular form of the demonstrative pronoun meaning this.

It matches množství, because množství is a neuter singular noun. So:

• ten = this/that for masculine
• ta = this/that for feminine
• to / toto = this/that for neuter

Here toto množství means this amount or this quantity.

After množství (amount, quantity), Czech normally uses the genitive case.

So:

• informace = information / piece of information
• informací = of information / of pieces of information (genitive plural)

This is very common in Czech:

• množství vody = an amount of water
• spousta lidí = lots of people
• málo času = little time

So množství informací literally works like an amount of information.

Czech often treats informace as a countable noun in contexts where English uses the uncountable noun information.

So Czech can say:

• hodně informací = a lot of information
• málo informací = little information
• několik informací can appear in some contexts, though often několik údajů / zpráv / informací depends on meaning

Even though English usually says information as uncountable, Czech commonly uses the plural form informací after quantity expressions.

Because the grammatical subject is toto množství.

The head noun is množství, which is:

• singular
• neuter

So the verb agrees with množství, not with informací.

That is why you get:

• Toto množství informací je důležité.

not

• Toto množství informací jsou důležité.

This is similar to English phrases like This amount of data is important, where amount controls the verb.

Because the adjective must agree with the noun it describes: množství.

Since množství is:

• neuter
• singular

the predicate adjective after je takes the neuter singular form:

• masculine singular: důležitý
• feminine singular: důležitá
• neuter singular: důležité

So:

• Ten problém je důležitý.
• Ta otázka je důležitá.
• To množství je důležité.

Toto is correct, but it can sound a bit more formal, careful, or written.

In everyday spoken Czech, people often say:

• Tohle množství informací je důležité.
• To množství informací je důležité.

Very roughly:

• toto = more formal / standard / emphatic
• tohle = common in speech, this
• to = can also mean this/that depending on context

So your sentence is perfectly good Czech, but not the most casual spoken style.

It is in the nominative, because it is the subject of the sentence.

You can see the structure like this:

• Toto množství informací = the subject
• je = is
• důležité = important

So:

• toto = nominative neuter singular
• množství = nominative neuter singular
• informací = genitive plural

Yes. Czech word order is more flexible than English, because case endings show grammatical roles.

For example, these are possible:

• Toto množství informací je důležité.
• Důležité je toto množství informací.

The basic version you were given is neutral and straightforward. A changed word order usually changes emphasis, not the core meaning.

For example:

• Důležité je toto množství informací. = emphasizes important
• Toto množství informací je důležité. = neutral statement

Yes, množství is a common Czech noun meaning amount, quantity, or volume depending on context.

It is:

• neuter
• usually grammatically singular in this type of sentence

Its ending -í is typical of many neuter nouns, though you should not rely on endings alone in every case.

Because it is neuter singular, it causes:

• toto množství
• je důležité

Yes, and that is useful to know.

Depending on context:

• informace can mean information
• jedna informace can mean one piece of information
• informace / informací in plural can mean pieces of information, details, or just information in a broader sense

So in this sentence, informací does not necessarily mean separate individual facts one by one. It can simply be the normal Czech way to express information after a quantity noun.

A very natural spoken version would be:

• Tohle množství informací je důležité.

Other natural variants include:

• To množství informací je důležité.
• Takové množství informací je důležité. = Such an amount of information is important

Your original sentence is fully correct; these are just style differences.

A rough pronunciation is:

• důležité ≈ doo-le-zhih-teh

A few key points:

• ů is a long oo sound
• ž sounds like the s in measure
• é is a long eh sound

So the word is pronounced approximately doo-le-zhih-teh, with clear vowels and no English-style reduction.

Yes. That is a good literal way to understand the structure:

• toto = this
• množství = quantity / amount
• informací = of information
• je důležité = is important

So grammatically, This quantity of information is important is a very helpful model, even if the most natural English translation might sometimes be This amount of information is important.