Learn Hardcore Dutch: Mijn spier trilt omdat ik te lang heb getypt en niet heb gerekt. - My muscle trembles because I have typed for too long and did not stretch.

In Dutch subordinate clauses (like those introduced by omdat), all the verbs move to the clause-final “verb cluster,” but the order inside that cluster can vary:

1–2 order: auxiliary before participle — omdat ik te lang heb getypt
2–1 order: participle before auxiliary — omdat ik te lang getypt heb

Both are correct in Standard Dutch. The 1–2 order is very common in the Netherlands; the 2–1 order is common in Flanders. Pick one and try to keep the order consistent within your sentence.

In the second part, do I have to repeat the subject or the auxiliary? Are there other correct ways to phrase that part?

You can handle the coordination in several correct ways:

As written (auxiliary repeated; subject omitted): omdat ik te lang heb getypt en niet heb gerekt.
One auxiliary at the very end: omdat ik te lang getypt en niet gerekt heb.
2–1 order for both parts: omdat ik te lang getypt heb en niet gerekt heb.
Repeating the subject (less common, used for emphasis/clarity): omdat ik te lang heb getypt en ik niet heb gerekt.

All are grammatical. Aim for parallelism (same internal order on both sides of “en”) for the smoothest style.

Why is niet placed before heb gerekt? Could I say it differently?

In subordinate clauses, negation niet comes before the whole verb cluster:

With 1–2 order: omdat ik niet heb gerekt
With 2–1 order: omdat ik niet gerekt heb

In a main clause, you’d say: Ik heb niet gerekt. What you should not say is: omdat ik heb niet gerekt (wrong placement of niet).

Why do we use hebben (heb) and not zijn in the perfect tense here?

Dutch uses:

zijn with verbs of movement or change of state (and a small set of exceptions): Ik ben gegaan, Ik ben gebleven, Ik ben geworden, Ik ben gevallen, etc.
hebben with transitive verbs and most activities: typen, rekken, werken, slapen, etc.

Since both typen and rekken are activities (not motion or change-of-state verbs), you use hebben: ik heb getypt, ik heb gerekt.

Can I use want instead of omdat? What changes?

Yes, but note the differences:

omdat starts a subordinate clause (verb cluster at the end):
Mijn spier trilt omdat ik te lang (getypt heb / heb getypt) en niet (gerekt heb / heb gerekt).
want is a coordinating conjunction and keeps normal main-clause word order (V2):
Mijn spier trilt, want ik heb te lang getypt en (ik) heb niet gerekt.

A comma before want is standard; before omdat it’s optional (see punctuation below).

Why is it spelled getypt with a final t? Why not getyped or getypt with d?

Because typen is a regular weak verb. Dutch uses the “soft ketchup/’t kofschip” rule to choose -t vs -d for weak past forms:

If the stem ends in a voiceless consonant from the set t, k, f, s, ch, p, you get -t.
Stem of typen is typ (ends in voiceless p) → past: typte, participle: ge-typ-t → getypt.

So: ik typte, ik heb getypt (never “getyped”).

Is gerekt the right verb for “stretched”? What about strekken, uitrekken, or the loanword stretchen?

rekken is the standard sports/physio verb “to (do) stretching”: Ik heb (mijn spieren) gerekt. Saying ik heb niet gerekt is perfectly idiomatic.
strekken means “to straighten/extend”: je arm strekken (to extend your arm). It’s not the usual word for doing stretching exercises.
uitrekken is “to stretch yourself out” (like after waking) or “to take off (clothes)” in other contexts: zich uitrekken ≈ to stretch one’s body luxuriously.
The loanword stretchen is common in gyms; its participle is often written gestretcht. Both rekken and stretchen are understood; rekken reads more natively.

Should it be te lang or te veel here?

te lang = too long (excessive duration)
te veel = too much (excessive amount)

If you mean you spent too much time typing, use te lang. If you mean you typed an excessive amount of text, use te veel. Both are possible in different contexts.

Do I need a preposition like “for” (Dutch voor) to say “for too long”?

No. You just say te lang without a preposition:

Correct: omdat ik te lang heb getypt
Incorrect: omdat ik voor te lang heb getypt

Is Mijn spier trilt idiomatic? Should it be plural?

It’s fine. Mijn spier trilt focuses on a specific muscle that’s twitching. If more than one is involved, say Mijn spieren trillen. You’ll also hear body-part-specific versions like Mijn ooglid trilt (my eyelid is twitching).
Other natural ways to describe it include: Mijn spier trekt samen (contracts) or Ik heb een spiertrekking (a muscle twitch/spasm), depending on the sensation.

Could I use the simple past instead of the perfect? For example, … omdat ik te lang typte?

Grammatically yes, but stylistically Dutch often prefers the present perfect for recent, relevant past actions, especially in speech:

Very natural: Mijn spier trilt omdat ik te lang heb getypt en niet heb gerekt.
Simple past is more “story-like” and pairs best with a past main clause:
Mijn spier trilde omdat ik te lang typte en niet rekte.

Using a present main clause with a simple-past cause sounds less idiomatic in everyday speech.

Do I need a comma before omdat?

It’s optional when the subordinate clause follows the main clause. Many writers omit it in short, clear sentences:

Without comma (common): Mijn spier trilt omdat …
With comma (also fine): Mijn spier trilt, omdat …

Never put a comma between omdat and its subject (omdat, ik … is wrong).

How do I pronounce tricky parts like getypt and gerekt?

Approximate pronunciations (Netherlands Dutch):

Mijn [mɛi̯n]
spier [spir] (long “ie” like English “ee”)
trilt [trɪlt]
omdat [ɔmˈdɑt]
getypt [ɣəˈtipt] (the Dutch g is a throaty sound; the y = “ie”)
gerekt [ɣəˈrɛkt]
niet [nit]

Tip: keep the final consonants crisp (no devoicing to “d” at the end: say [t] in getypt, gerekt).

Could I say Mijn spier is aan het trillen instead of Mijn spier trilt?

You can, and it emphasizes the ongoing nature of the action. However, for brief or intermittent twitches, the simple present (Mijn spier trilt) is the default and usually sounds more natural. Use is aan het trillen when you want to stress “right now, continuously.”