افتحي الفرن بعد عشر دقائق، لكن لا تضعي القدر قرب النار.

Because the sentence is addressing one female person.

In Modern Standard Arabic, commands and present-tense verb forms change depending on the gender and number of the person addressed.

• افتحي = open! said to one woman
• لا تضعي = don’t put! said to one woman

Compare:

• to one man: افتحْ / لا تضعْ
• to one woman: افتحي / لا تضعي
• to two people: افتحا / لا تضعا
• to a group: افتحوا / لا تضعوا

So the sentence is specifically speaking to أنتِ.

افتحي is the imperative of the verb فتح (to open) for one female addressee.

A simple way to see it:

• basic verb: فتح
• masculine singular command: افتحْ
• feminine singular command: افتحي

So Arabic takes the command form and adds -ي for you (feminine singular).

The initial ا in افتحي is a helping vowel called hamzat al-waṣl. It allows the word to begin smoothly in pronunciation.

In Arabic, negative commands are usually made with:

• لا
  • present tense in the jussive

So instead of a separate negative imperative, Arabic uses a prohibition structure:

• تضعين = you (feminine) put / are putting
• لا تضعي = don’t put

This لا is called لا الناهية (the prohibitive lā).

So:

• ضعي = put!
• لا تضعي = don’t put!

Because after لا الناهية, the verb goes into the jussive, and with this kind of verb form, the final ن drops.

For you (feminine singular), the normal present form is:

• تضعين

After prohibitive لا, it becomes:

• لا تضعي

This happens because تضعين belongs to the set called the five verbs (الأفعال الخمسة), and in the jussive these forms lose the final ن.

So:

• indicative: تضعين
• jussive after لا: تضعي

This is because of the number rule for 3–10 in Arabic.

The singular of minutes is دقيقة, and دقيقة is feminine.
With numbers from 3 to 10, Arabic uses the form of the number with the opposite gender.

Since دقيقة is feminine, Arabic uses عشر here, not عشرة.

So:

• دقيقة = feminine singular noun
• therefore ten appears as عشر

This is a very common Arabic pattern, even though it feels backwards to English speakers.

Because with numbers 3 through 10, the counted noun is usually:

• plural
• and normally genitive

So Arabic says:

• عشر دقائق = ten minutes

not:

• عشر دقيقة

This is another standard number rule:

• one and two behave differently
• 3–10 usually take a plural counted noun

It means after ten minutes, and it gives a time expression.

The key word is بعد = after.

In this sentence, بعد is followed by a noun phrase telling after how long:

• بعد عشر دقائق = after ten minutes

You can think of it as:

• افتحي الفرن = open the oven
• بعد عشر دقائق = after ten minutes

So the phrase tells when the action should happen.

Because قرب can function as a word meaning near / close to in a direct way.

So:

• قرب النار = near the fire

This is a compact Arabic structure.
A more adjective-like version is also possible:

• قريب من النار = close to the fire

The difference is mainly structural:

• قرب النار uses قرب as an adverbial/preposition-like noun
• قريب من النار uses the adjective قريب plus من

In this sentence, قرب النار is very natural.

The pronunciation is different because of moon letters and sun letters.

• الفرن: the letter ف is a moon letter, so the ل is pronounced
  → al-furn

• النار: the letter ن is a sun letter, so the ل assimilates to the next consonant
  → an-nār

So although both words are written with ال, they are pronounced differently.

Because وضع is a verb whose root begins with و, and in the present tense that و disappears.

You see:

• past: وضع = he put
• present: يضع = he puts
• present for you (feminine): تضعين
• prohibitive: لا تضعي

So the missing و is normal.
It is part of how this verb behaves in Arabic.

This is why the form is تضعي, not something like توضعي.

In unvowelled Arabic writing, the spelling can be the same, but the meaning is distinguished by context and, if shown, by vowels.

• القِدر = the pot
• القَدَر = fate / destiny

In this sentence, the context is cooking:

• oven
• pot
• fire

So القدر clearly means the pot here.

If fully vowelled, it would be:

• القِدر

A fully vowelled version could be:

اِفتَحي الفُرْنَ بعدَ عَشْرِ دَقائِقَ، لكنْ لا تَضَعي القِدْرَ قُرْبَ النارِ.

A few useful notes:

• In normal Arabic writing, these short vowels are usually not written.
• In careful formal reading, the endings may be pronounced.
• In pause, speakers often reduce or stop before fully pronouncing every case ending.

One advanced detail: دقائق is a type of plural that may take fatḥa where you might expect kasra, so in fully vowelled text you may see دقائقَ even though the phrase is functioning genitively. That is normal Arabic grammar, not a typo.