Mám velký strach.

Because Czech often expresses feelings with mít + a noun, literally to have something.

So:

• Mám strach. = literally I have fear
• natural English meaning: I am afraid

This is a very common Czech pattern. English often uses to be for states, but Czech may use to have instead.

Compare:

• Mám hlad. = I am hungry / literally I have hunger
• Mám žízeň. = I am thirsty / literally I have thirst
• Mám strach. = I am afraid / literally I have fear

Mám is the 1st person singular present tense of mít (to have).

So:

• já mám = I have
• ty máš = you have
• on/ona má = he/she has

In this sentence, mám tells you the subject is I, so Czech usually does not need the pronoun já.

• Mám velký strach. = I am very afraid
• Já mám velký strach. = also possible, but já adds emphasis

Strach is a masculine inanimate noun, and here it is the direct object of mám, so it is in the accusative case.

For masculine inanimate nouns, the accusative singular is often the same as the nominative singular. The adjective also matches it.

So:

• nominative: velký strach
• accusative: velký strach

That is why the form stays velký.

If the noun were different, the adjective ending might change. For example:

• Mám velkou radost. = I am very happy / I have great joy
  • here radost is feminine, so accusative uses velkou

Yes, absolutely. Mám strach is a very common and natural expression.

You can think of it as one of the standard ways to express fear. Czech also uses:

• Bojím se. = I’m afraid / I’m scared
• Mám strach. = I’m afraid / I have fear

Both are common, but they are built differently:

• mít strach = to have fear
• bát se = to fear / to be afraid

They are often very close in meaning, but there can be a small difference in feel.

• Mám strach often emphasizes the feeling of fear itself.
• Bojím se often feels a bit more verbal and can more easily take an object or clause: I’m afraid of...

Examples:

• Mám strach. = I’m scared.
• Bojím se psa. = I’m afraid of the dog.
• Mám strach z psů. = I’m afraid of dogs.

In many situations, either can work. A learner should understand both.

Yes, velký literally means big or large, so velký strach literally means big fear.

Czech often uses an adjective where English would use an adverb like very. So:

• Mám strach. = I’m afraid.
• Mám velký strach. = I’m very afraid / I’m really scared.

It is a natural Czech expression.

Other intensifying options are also possible, for example:

• Mám opravdu velký strach. = I’m really very afraid.
• Mám hrozný strach. = I’m terribly scared.
• Moc se bojím. = I’m very scared.

Yes. Depending on context, Mám velký strach can refer to:

• immediate fear in a situation: I’m very scared
• a strong ongoing fear or anxiety: I have great fear

So the sentence can sound a bit broader or heavier than just a quick reaction.

If someone suddenly sees something frightening, they might also simply say:

• Bojím se! = I’m scared!
• Mám strach! = I’m scared!

But Mám velký strach can sound a bit more intense or serious.

Because Czech has no articles.

So Czech does not have separate words corresponding to English a/an and the. You understand definiteness from context.

That means:

• Mám strach. can mean I have fear, I have a fear, or more naturally I am afraid
• Mám velký strach. can mean I have great fear or I am very afraid

The exact English wording depends on context.

Yes. Czech word order is fairly flexible, because grammatical roles are shown by endings more than by position.

The most neutral order here is:

• Mám velký strach.

But other orders are possible for emphasis, for example:

• Velký strach mám. = emphasis on great fear
• Strach mám velký. = also possible, but more marked

A learner should normally use Mám velký strach unless there is a special reason to emphasize something.

A very common pattern is:

• mít strach z
  • genitive

Examples:

• Mám strach z psa. = I’m afraid of the dog.
• Mám strach z psů. = I’m afraid of dogs.
• Mám strach z toho, co se stane. = I’m afraid of what will happen.

So your sentence can be expanded easily:

• Mám velký strach z budoucnosti. = I’m very afraid of the future.

Roughly, strach sounds like strahkh, with the Czech ch pronounced like the ch in Scottish loch or German Bach, not like English ch in chair.

A rough pronunciation of the whole sentence is:

• Mám velký strach.
• approximately: maam VEL-kee strakh

A few notes:

• á in mám is a long vowel
• ý in velký is also long
• ch is one sound, not k+h

Yes, definitely.

• Mám strach. = I’m afraid.
• Mám velký strach. = I’m very afraid / I have great fear.

Without velký, the sentence is simpler and more neutral. Adding velký makes the fear stronger or more emphatic.