Learn Hardcore Czech: Doktorka pomůže i mojí dceři, protože má stejný problém. - The lady doctor will also help my daughter, because she has the same problem.

i doktorka pomůže mojí dceři – even the doctor will help my daughter
doktor pomůže i mojí dceři – the doctor will help my daughter as well (in addition to someone else)

So i comes before mojí dceři because the idea is: besides someone else, the doctor will help my daughter too.

Why is it pomůže and not pomáhá? Both come from to help, right?

Yes, both are from the verb pomoci / pomáhat (to help), but they differ in aspect and time:

pomáhá – imperfective, present tense
- means is helping / helps (regularly)
- focuses on an ongoing or repeated action
pomůže – perfective, morphologically "present", but with future meaning
- means will help (once / in that specific situation)
- focuses on a completed, single act

In this sentence, the idea is a specific future act: the doctor will help my daughter too, so pomůže is used.

If you said:

Doktorka pomáhá mojí dceři.
it would mean The doctor helps my daughter / is helping my daughter (in general / repeatedly).

Why is it mojí dceři and not moje dcera?

Because of case.

The verb pomoci / pomáhat takes the dative case (answers the question komu? čemu? – to whom? for whom?).

moje dcera – nominative (who? what?)
mojí dceři – dative (to whom?)

In the sentence:

(Doktorka) pomůže komu? – mojí dceři.
– (The doctor) will help whom? – my daughter (dative).

So mojí dceři is the correct dative form:

dcera → dceři (dative singular)
moje → mojí (feminine dative singular)

What case is dceři, and how is it formed from dcera?

dceři is dative singular of dcera (daughter).

Declension:

Nominative: dcera (who? what? – daughter)
Dative: dceři (to whom? – to the daughter)

The ending -a changes to -i in the dative singular for many feminine nouns of this type (like žena → ženě, kolega → kolegovi, etc., though patterns differ somewhat).

Because pomůže takes dative, we need dceři.

What is the difference between moje, mojí, and moji?

These are different case and gender forms of the possessive adjective můj (my).

Relevant here:

moje dcera – nominative singular feminine
moji dceru – accusative singular feminine (variant; more neutral in speech is moji dceru / mou dceru)
mojí dceři – dative singular feminine (our sentence)

Notice the spelling:

moji (short i) – accusative feminine, nominative plural masculine animate, etc.
mojí (long í) – dative (and locative) feminine singular

So in our sentence mojí with a long í is correct because it must agree with dceři in case (dative).

Why is it protože má stejný problém and not something like protože má stejným problémem?

The verb mít (to have) takes a direct object in the accusative case.

mít co? – to have what?

So:

má stejný problém – stejný problém is accusative (direct object)
- problém is masculine inanimate; accusative = nominative: problém
- adjective agrees: stejný problém

If you said stejným problémem, that would be instrumental (with what / by means of what), which doesn’t fit after mít.

Who does má stejný problém refer to – the doctor or the daughter?

Grammatically, Czech allows some ambiguity here, because the subject is just understood from context and not repeated.

protože má stejný problém literally = because (she) has the same problem

The she could refer to:

the doctor, or
the daughter

Usually context makes it clear. If you wanted to be explicit, you could say:

… protože moje dcera má stejný problém. – because my daughter has the same problem.
… protože doktorka má stejný problém. – because the doctor has the same problem.

So in isolation, the clause could refer to either, and the listener uses context or world knowledge to decide.

Why is stejný masculine when it’s the daughter who has the problem (and dcera is feminine)?

Agreement in Czech is with the noun the adjective modifies, not with the person who owns it.

The adjective stejný modifies problém, not dcera.
problém is masculine inanimate, so the adjective must be masculine too: stejný problém.

The fact that the person having the problem (doctor or daughter) is feminine doesn’t affect the gender of problém.

Could you also say Doktorka pomůže také mojí dceři instead of i mojí dceři?

Yes, you can.

i and také / taky often mean also / too.

Nuances:

i is short, neutral, and often directly emphasizes the word it stands before.
také is a bit more formal/literary; taky is more colloquial.

Examples:

Doktorka pomůže i mojí dceři. – The doctor will help my daughter too.
Doktorka pomůže také mojí dceři. – Same meaning, slightly more formal.
Doktorka pomůže taky mojí dceři. – Colloquial, everyday speech.

Is the comma before protože obligatory in Czech?

Yes.

In Czech, a comma is generally used before conjunctions introducing subordinate clauses, such as:

protože (because)
když (when, if)
aby (so that)
že (that), etc.

So you write:

Doktorka pomůže i mojí dceři, protože má stejný problém.

Leaving out the comma would be considered incorrect in standard written Czech.

How do you pronounce dceři? It looks difficult.

dceři is pronounced roughly as: [d-tse-ři]

Breakdown:

dc – pronounced together like ts in cats (you start with a light d, but it merges into c = [ts])
e – like e in bet
ř – the famous Czech sound, something like r plus zh combined, vibrating (similar to the r in Dvořák)
i – like ee in see

So slowly: d-tse-ři, then smoother: dceři. Practising dc at the start helps.

Could I say Doktorka pomůže i moji dceru instead of mojí dceři?

No, that would be incorrect with pomůže.

moji dceru is accusative (direct object: I see my daughter – vidím moji dceru)
pomoci / pomáhat require dative: to help someone = pomoci komu?

So you must use mojí dceři (dative), not moji dceru (accusative):

✅ Doktorka pomůže mojí dceři.
❌ Doktorka pomůže moji dceru. (ungrammatical)