Learn Hardcore German: Nach der Schule gehe ich mit meinen Freundinnen ins Schwimmbad, um zu schwimmen. - After school I go to the swimming pool with my female friends in order to swim.

You can sometimes drop the article with time expressions (e.g. nachmittags = in the afternoon), but with Schule people normally keep the article:

Natural: Nach der Schule gehe ich nach Hause.
Odd/unnatural: Nach Schule gehe ich nach Hause.

Could I also say Ich gehe nach der Schule mit meinen Freundinnen ins Schwimmbad? Why does the sentence start with Nach der Schule?

Yes, you can absolutely say:

Ich gehe nach der Schule mit meinen Freundinnen ins Schwimmbad, um zu schwimmen.

German has a verb-second rule in main clauses:

The conjugated verb (here: gehe) must be in position 2.
Position 1 can be the subject (ich) or some other element, like a time expression (nach der Schule).

So both are correct:

Nach der Schule (position 1) gehe (position 2) ich …
Ich (position 1) gehe (position 2) nach der Schule …

Starting with Nach der Schule puts emphasis on the time (“after school” is the important information). Starting with Ich emphasizes the subject instead.

Why is it gehe (present tense) and not something like “will go” (future tense) like in English?

German uses the present tense much more often than English to talk about the future, when the context makes the time clear.

Nach der Schule gehe ich …
= “After school I am going / will go …”

You only need the future form (werde gehen) in German if you want to make the futurity extra explicit or contrast it:

Nach der Schule werde ich nicht nach Hause gehen, sondern ins Schwimmbad.

But in everyday speech:

Nach der Schule gehe ich … is the natural choice.

Why mit meinen Freundinnen and not mit meine Freundinnen or mit meinen Freunde?

Two things are going on here: case and gender/number.

Case: dative after “mit”
The preposition mit always takes the dative case.
The possessive mein- in dative plural is meinen:
- Nominative plural: meine Freundinnen (my friends – all female)
- Dative plural: mit meinen Freundinnen
So:
- ❌ mit meine Freundinnen – wrong case
- ✅ mit meinen Freundinnen – correct dative plural
Gender/number: Freund vs Freunde vs Freundinnen
- ein Freund = a (male) friend
- eine Freundin = a (female) friend
- Freunde = male friends or mixed group
- Freundinnen = only female friends

Since the sentence clearly refers to female friends only, it uses Freundinnen (plural feminine), and in the dative plural with mit that gives:

✅ mit meinen Freundinnen

What is the difference between Freunde and Freundinnen? Could I just say Freunde?

Freunde = male friends or a mixed group (male + female).
Freundinnen = exclusively female friends.

So:

If your group is all girls:
- More precise: meine Freundinnen
- Grammatically okay but less precise: meine Freunde (this sounds like there might be males in the group)
If it’s mixed or all male:
- meine Freunde is the normal choice.

In day-to-day conversation, people sometimes say Freunde even if the group happens to be all female, but if you want to stress that they’re all girls, you use Freundinnen.

Why is it ins Schwimmbad and not im Schwimmbad or in das Schwimmbad?

Three forms:

ins Schwimmbad
- ins = contraction of in das (in + the, accusative).
- Used with motion towards a place (direction).
- Ich gehe ins Schwimmbad. = I’m going (into) the swimming pool / pool building.
im Schwimmbad
- im = contraction of in dem (in + the, dative).
- Used with location (where you are).
- Ich bin im Schwimmbad. = I am at the pool.
in das Schwimmbad (full form)
- Grammatically correct, but in spoken German usually shortened to ins Schwimmbad.
- Same meaning as ins Schwimmbad.

In your sentence, you are talking about going to the pool (movement), so you need the accusative (direction) form:

✅ ins Schwimmbad gehen

Why is there a comma before um?

The part um zu schwimmen is a subordinate infinitive clause expressing purpose (“in order to swim”).

In German, um … zu + infinitive clauses must be separated by a comma from the main clause:

Nach der Schule gehe ich … ins Schwimmbad, um zu schwimmen.

General rule:
Whenever you have an “um … zu” clause, “ohne … zu” clause, or “anstatt … zu” clause, you put a comma before it.

What does um zu schwimmen literally mean, and why do we need both um and zu?

Literal breakdown:

um … zu + infinitive = “in order to …”

Parts:

um introduces the idea of purpose / intention.
zu schwimmen is the infinitive construction (“to swim”), with zu before the infinitive schwimmen.

So:

… ins Schwimmbad, um zu schwimmen.
= “… to the pool in order to swim.”

You can think:

um ≈ “in order”
zu schwimmen ≈ “to swim”

Both um and zu are needed for this standard “in order to” structure.

Could we leave out um and just say … ins Schwimmbad, zu schwimmen?

No, that sounds incorrect or at least very unnatural in this sentence.

✅ … ins Schwimmbad, um zu schwimmen.
❌ … ins Schwimmbad, zu schwimmen.

In German, to express purpose with an infinitive in a normal way, you almost always use um … zu.

A bare zu + infinitive by itself is used in other structures:

After certain verbs:
- Ich versuche, schwimmen zu lernen. (I’m trying to learn to swim.)
As part of noun phrases:
- die Möglichkeit, schwimmen zu gehen (the possibility of going swimming)

But for “in order to swim” after a full clause, you want um zu schwimmen.

Where does the verb go in an um … zu clause? Could I say um zu schwimmen gehe ich ins Schwimmbad?

In an um … zu clause:

The infinitive verb (here: schwimmen) goes at the end.
zu stands directly in front of the infinitive.

So:

✅ um zu schwimmen
❌ um schwimmen zu
❌ um zu gehe schwimmen

Your suggestion changes the structure:

Um zu schwimmen gehe ich ins Schwimmbad.

This is actually correct German, but now “Um zu schwimmen” is at the beginning as a purpose clause, followed by the main clause:

Position 1: Um zu schwimmen
Position 2 (verb): gehe
Rest: ich ins Schwimmbad

So yes, “Um zu schwimmen, gehe ich ins Schwimmbad.” is fine. The verb schwimmen stays at the very end of the um … zu part.

Why are Schule, Freundinnen, and Schwimmbad capitalized?

In German, all nouns are capitalized.

Schule – noun (school)
Freundinnen – noun (friends, feminine plural)
Schwimmbad – noun (swimming pool)

This is true regardless of position in the sentence:

Schule, even in the middle, still has a capital S.
Adjectives and verbs are usually not capitalized, unless they’re turned into nouns (e.g. das Schwimmen = swimming as a noun).

Why is Schwimmbad neuter (das Schwimmbad, ins Schwimmbad) and Schule feminine (die Schule, nach der Schule)? Is there a rule?

German grammatical gender is only partly predictable. Some patterns help:

Many nouns ending in -e are feminine:
- die Schule, die Lampe, die Blume
Many compound nouns ending in -bad (bath/pool) are neuter:
- das Schwimmbad, das Hallenbad

But there is no universal rule; a lot of gender must simply be memorized with the noun:

Learn die Schule (fem.)
Learn das Schwimmbad (neut.)

That’s why dictionaries always show nouns with their article: die Schule, das Schwimmbad, die Freundin, der Freund, etc.

Could I use fahren instead of gehen here: Nach der Schule fahre ich mit meinen Freundinnen ins Schwimmbad?

Yes, you can, and the meaning changes slightly:

gehen = go on foot (“walk”)
fahren = go by vehicle (car, bus, bike, train, etc.)

So:

Nach der Schule gehe ich ins Schwimmbad.
→ Suggests you walk to the pool.
Nach der Schule fahre ich ins Schwimmbad.
→ Suggests you travel there using some transport.

Both are grammatically correct; you choose depending on how you get there.

Do all the prepositions in this sentence always take the same case? (nach, mit, in)

In this sentence:

nach der Schule → nach
- dative
mit meinen Freundinnen → mit
- dative
ins Schwimmbad → in
- accusative (because of motion)

Case rules:

nach
- With time (“after”) or with most places (countries, cities):
  - Always dative:
    - nach der Schule, nach dem Essen, nach dem Film
mit
- Always dative:
  - mit meinen Freundinnen, mit dem Bus, mit meiner Mutter
in
- This is a two-way preposition (Wechselpräposition):
  - Dative for location (where?) → im Schwimmbad (in dem Schwimmbad)
  - Accusative for direction (where to?) → ins Schwimmbad (in das Schwimmbad)

So:

nach and mit: always dative.
in: dative or accusative, depending on location vs motion.