Bij de kapper heb ik gezegd dat mijn pony niet te kort mocht worden.

Bij de kapper means at the hairdresser's or at the hairdresser.

Dutch often uses bij with people, professions, and businesses to mean at the place of or with that person/service:

• bij de dokter = at the doctor’s
• bij de bakker = at the bakery / at the baker’s
• bij de kapper = at the hairdresser’s

So this is a very normal idiomatic use of bij.

Because Dutch main clauses normally follow the verb-second rule.

If the sentence starts with something other than the subject, the finite verb still has to come second, and the subject moves after it.

So:

• Ik heb gezegd ... = neutral order
• Bij de kapper heb ik gezegd ... = the phrase bij de kapper comes first, so heb must come next

This is called inversion.

Yes, but not the animal.

In Dutch, pony can mean fringe or bangs in a hairstyle. So:

• mijn pony = my bangs / my fringe

This is a very common word in Dutch hair-related contexts.

Because kort is used predicatively here, not directly before a noun.

In this sentence:

• mijn pony ... te kort mocht worden

the adjective describes the result/state of mijn pony after worden. Predicative adjectives in Dutch do not take the -e ending.

Compare:

• een te korte pony = a too-short fringe/bangs
  
  • adjective before the noun, so -e
• mijn pony werd te kort = my bangs became too short
  
  • adjective after the verb, so no -e

Dat introduces a subordinate clause and means that.

The sentence has two parts:

• Bij de kapper heb ik gezegd = At the hairdresser’s I said
• dat mijn pony niet te kort mocht worden = that my bangs were not to become too short

After verbs like zeggen, denken, weten, and horen, Dutch often uses dat to introduce what was said, thought, known, or heard.

Because after dat, Dutch uses subordinate clause word order, where verbs usually go to the end.

So:

• main clause: Ik heb gezegd
• subordinate clause: dat mijn pony niet te kort mocht worden

In that subordinate clause, the verb cluster goes at the end:

• mocht worden

This is one of the most important word-order patterns in Dutch.

Mocht is the past tense of mogen.

Here it does not simply mean was allowed to in the most literal English sense. In this kind of context, it means something like:

• was not allowed to
• was not supposed to
• must not

So mijn pony niet te kort mocht worden literally means something like:

• my bangs were not allowed to become too short

A more natural English translation would often be:

• I said my bangs shouldn’t be cut too short.

Worden means to become.

Dutch often uses worden + adjective to talk about a change of state:

• te kort worden = become too short
• oud worden = become old
• boos worden = become angry

So mijn pony niet te kort mocht worden literally means my bangs were not allowed to become too short.

In context, that means the haircut should not make the bangs too short.

It could, but it does not have to.

Dutch can express the idea in a more direct cutting-focused way:

• ... dat mijn pony niet te kort geknipt mocht worden

That means more explicitly:

• ... that my bangs were not allowed to be cut too short

But niet te kort mocht worden is also natural, because the result is what matters: the bangs must not end up too short.

So the original sentence focuses on the result, not the cutting action itself.

It is past tense, but it also gives a certain nuance.

Because the speaker is talking about something they said in a past situation at the hairdresser, mocht fits that past frame well.

It can also sound a bit softer or more indirect than stronger alternatives.

Compare:

• niet te kort mag worden
  
  • more like a present rule: must not become too short
• niet te kort mocht worden
  
  • looking back at what was allowed in that past situation
• niet te kort moest worden
  
  • stronger sense of necessity: must not become too short / had to not become too short

So mocht works well for a polite instruction or restriction in a past context.

Yes.

• Ik heb bij de kapper gezegd dat ...
• Bij de kapper heb ik gezegd dat ...

Both are correct.

The difference is mainly emphasis:

• Ik heb bij de kapper gezegd ... = more neutral
• Bij de kapper heb ik gezegd ... = puts extra focus on the setting at the hairdresser’s

So the original sentence highlights where this happened.