U juhu stavljam malo papra, ali sok od limuna mi je danas previše kiseo.

Because u can take different cases depending on meaning.

• u + accusative = movement into something
• u + locative = location in something

Here, stavljam means I am putting, so there is movement into the soup:

• u juhu = into the soup

Compare:

• Stavljam papar u juhu. = I’m putting pepper into the soup.
• Papar je u juhi. = The pepper is in the soup.

So juhu is accusative singular of juha.

This is about aspect, which is very important in Croatian.

• stavljati / stavljam = imperfective
• staviti / stavim = perfective

Stavljam is used for an action that is ongoing, repeated, or viewed as a process:

• U juhu stavljam malo papra. = I’m putting a little pepper into the soup.

If you used stavim, it would sound more like a completed single action, or in the present tense it often has a future-like sense in many contexts.

So here stavljam is the natural choice for describing what you are doing.

Because quantity words like malo are normally followed by the genitive.

So:

• malo papra = a little pepper

Here:

• malo = a little / a small amount
• papra = genitive singular of papar

This is very common in Croatian:

• malo vode = a little water
• malo soli = a little salt
• malo šećera = a little sugar

So malo papra is the normal pattern.

Papra is the genitive singular form of papar (pepper).

Basic forms:

• nominative: papar
• genitive: papra
• accusative: papar (for this inanimate noun)

In the sentence, you need the genitive because of malo:

• malo papra

This is one of those forms that learners just have to get used to, because the stem changes a bit from papar to papra.

This is a very common Croatian structure:

• X od Y = X of Y / X made from Y

So:

• sok od limuna = lemon juice

Here, od takes the genitive, so limuna is genitive singular of limun.

You will see this pattern a lot:

• čaša vode = a glass of water
• boca vina = a bottle of wine
• sok od naranče = orange juice

Croatian can also use an adjective-like form in some cases, but sok od limuna is completely normal.

Yes. Both are possible.

• sok od limuna = juice of lemon / lemon juice
• limunov sok = lemon juice

The version with od + genitive is very transparent and common.
The possessive-adjective version (limunov) is also natural.

In many situations, the two mean almost the same thing. A learner should understand both.

Mi is the unstressed dative form of ja (to me / for me).

So:

• sok od limuna mi je danas previše kiseo

literally includes the idea:

• the lemon juice is too sour to me / for me today

In natural English, we often just say:

• The lemon juice is too sour for me today
• or simply The lemon juice tastes too sour today

The mi adds a personal point of view. It shows that this is how it seems or tastes to the speaker.

Because mi and je are clitics: short unstressed words that usually go near the beginning of the clause, often after the first stressed word or phrase.

So this is natural:

• Sok od limuna mi je danas previše kiseo.

The noun phrase sok od limuna comes first, and then the clitics mi je appear.

Croatian word order is flexible, but clitics have special placement rules. For example, you could also say:

• Danas mi je sok od limuna previše kiseo.

That shifts the emphasis toward today.

So the sentence’s word order is not random; it follows normal Croatian clitic placement and information focus.

Because kiseo agrees with sok, which is:

• masculine
• singular
• nominative (the subject of je)

So the adjective must also be masculine singular nominative:

• sok → kiseo

Compare:

• juha je kisela = the soup is sour
• vino je kiselo = the wine is sour
• sok je kiseo = the juice is sour

So the ending changes to match the noun.

It is a normal masculine singular form, but it can look strange at first.

The adjective is based on the idea kis-, and the masculine nominative singular form is:

• kiseo

Other forms are easier to recognize:

• kisela = feminine singular
• kiselo = neuter singular
• kiseli / kisele = plural forms, depending on gender

So if juha is sour, it is kisela.
If sok is sour, it is kiseo.

Previše means too much / excessively / too.

In this sentence, it modifies the adjective:

• previše kiseo = too sour

So:

• kiseo = sour
• previše kiseo = too sour

It works like an adverb here, and it does not change form.

Yes, you often can.

• previše kiseo = too sour
• prekiseo = overly sour / too sour

The version with previše + adjective is very clear and works with almost any adjective.
The one-word form can sound a bit more compact.

So both are understandable and natural, though the sentence you were given uses the more analytic pattern previše kiseo.

Yes. Croatian word order is flexible, and danas can move depending on what you want to emphasize.

For example:

• Sok od limuna mi je danas previše kiseo.
• Danas mi je sok od limuna previše kiseo.

Both are natural. The second one puts stronger focus on today.

So the position of danas is not fixed in the way it often is in English.

Because Croatian does not have articles like English a/an/the.

So a noun like juha or sok does not need an article. Whether it means the soup, a soup, the juice, or some juice depends on context.

Learners from English often expect an article, but Croatian simply does not use one.