Learn Hardcore Czech: Cvičím jen málo, ale moje kamarádka běhá pravidelně každý týden. - I exercise only a little, but my female friend runs regularly every week.

You only say já cvičím when you want to emphasize I (not someone else), e.g.:
Já cvičím jen málo, ale ona běhá pravidelně. = I exercise only a little, but she runs regularly.

What’s the difference between “cvičit” and “běhat”? Aren’t they both “to exercise”?

They’re related to physical activity, but not the same:

cvičit = to exercise, to work out, to do physical training/gym-type exercise
- Cvičím jen málo. = I don’t exercise much.
běhat = to run (habitually, repeatedly)
- Moje kamarádka běhá pravidelně. = My friend runs regularly.

So in this sentence:

cvičím is general exercise,
běhá is specifically running as a sport.

Why is it “jen málo” and not something like “málo jen”?

The usual and natural order is:

jen málo = only a little

jen (“only”) typically comes before the word or phrase it limits:

jen málo cvičím = I exercise only a little
jen já cvičím = only I exercise
mám jen jednu knihu = I have only one book

You could say Jen málo cvičím, but that changes the sentence rhythm and emphasis (focusing first on how little, then on what you do). Málo jen is not idiomatic here.

Why is it “moje kamarádka” and not “můj kamarádka”?

The possessive pronoun must agree with the noun’s gender and number.

kamarádka = (female) friend → feminine singular
- correct: moje kamarádka
kamarád = (male) friend → masculine animate singular
- correct: můj kamarád

So:

moje kamarádka = my (female) friend
můj kamarád = my (male) friend

The meaning of the sentence makes it clear the friend is female.

What is the difference between “kamarádka” and “přítelkyně”?

Both can translate as “friend,” but the nuance is different:

kamarádka
- default meaning: female friend, buddy, mate
- usually non-romantic unless the context says otherwise.
přítelkyně
- can mean female friend, but very often means girlfriend (romantic partner) in modern usage.

In this neutral sentence, kamarádka is the safe word for “female friend.”

Why is it “běhá” and not “běží”?

Czech verbs of motion often have two stems: one for repeated/habitual movement and one for a single / specific movement.

běhat → běhá (imperfective, iterative) = to run regularly, repeatedly
běžet → běží (imperfective, but single course of running) = to run (right now / one time)

In this sentence we talk about a habit:

Moje kamarádka běhá pravidelně každý týden.
= My friend runs regularly every week (habit).

If it were about a specific situation right now, you might say:

Moje kamarádka právě běží domů.
= My friend is (currently) running home.

Isn’t “pravidelně každý týden” redundant? “Regularly” and “every week” sound similar.

Yes, there is some overlap, but it’s still natural and not wrong. The nuance is:

pravidelně = in a regular, consistent pattern
každý týden = every week (tells you how often)

Together they emphasize both:

that it’s weekly
and that she does it consistently, not just “from time to time every week.”

You could also say only one of them, depending on what you want to stress:

Moje kamarádka běhá každý týden.
Moje kamarádka běhá pravidelně.

All are correct.

Why is the present tense used for a habitual action, as in “Cvičím… kamarádka běhá…”?

Czech present tense covers both:

English present simple (habit):
- Cvičím jen málo. = I (usually) don’t exercise much.
and English present continuous (now):
- Teď cvičím. = I am exercising (now).

There is no special progressive form in Czech. Context decides whether the meaning is habitual or right now. Here, words like jen málo, pravidelně, každý týden clearly show a habitual meaning.

Why is it “každý týden” and not “každém týdnu”?

Czech often uses accusative with time expressions to mean “every X / each X (repeatedly in time)”:

každý týden (accusative) = every week
každý den = every day
každý večer = every evening

v každém týdnu would be grammatically possible but sounds more like “in each week” in a more abstract or analytical sense, not a normal description of routine. For regular frequency, každý týden is the natural form.

Why do we need “ale” and a comma before it?

ale means “but” and connects two independent clauses:

Cvičím jen málo
(ale) moje kamarádka běhá pravidelně každý týden.

Czech usually places a comma before ale when it connects two clauses:

Nechci jít ven, ale musím. = I don’t want to go out, but I have to.
Cvičím jen málo, ale moje kamarádka běhá pravidelně každý týden.

So the comma is there for the same basic reason as in English: it separates two full clauses joined by “but / ale”.