Mandalina suyu çok soğuk olunca boğazım ağrıyor.

Mandalina suyu is a noun compound meaning tangerine juice.

In Turkish, compounds like X juice, X door, X color, etc. often use a special ending on the second noun. Here:

• mandalina = tangerine
• su = water / juice
• suyu = its juice / juice of X in a compound

So:

• mandalina suyu = tangerine juice
• compare:
  • elma suyu = apple juice
  • portakal suyu = orange juice

This -u/-ü/-ı/-i ending is very common in noun compounds.

Because mandalina suyu and mandalinanın suyu are not exactly the same structure.

• mandalina suyu = tangerine juice in a general, dictionary-style sense
• mandalinanın suyu = the juice of the tangerine

The version with -nın is more specific and sounds like you are talking about a particular tangerine.

So in everyday product/food names, Turkish usually prefers:

• portakal suyu = orange juice
• üzüm suyu = grape juice
• mandalina suyu = tangerine juice

Olunca comes from the verb olmak = to be / to become / to happen.

Here, soğuk olunca means something like:

• when it is cold
• when it gets cold
• if it is very cold
• once it is very cold

In this sentence, çok soğuk olunca gives the idea:

when tangerine juice is very cold / if it’s very cold

This -ınca / -ince / -unca / -ünce form often connects one situation to another:

• Eve gelince ararım. = When I get home, I’ll call.
• Yorgun olunca erken uyur. = When he’s tired, he sleeps early.

Both are possible in many situations, but they are slightly different in feel.

• soğukken = when it is cold / while it is cold
• soğuk olunca = when it becomes/is cold; when it is in the state of being cold, often with a cause-and-effect feeling

In this sentence, çok soğuk olunca boğazım ağrıyor sounds natural because it suggests:

when it is very cold, that causes my throat to hurt

So olunca works well for a condition that leads to a result.

Boğazım means my throat.

Breakdown:

• boğaz = throat
• boğazım = my throat

The -ım / -im / -um / -üm ending is a 1st person singular possessive suffix.

Examples:

• elim = my hand
• başım = my head
• gözüm = my eye
• boğazım = my throat

Turkish often uses possessive suffixes where English uses my.

Because Turkish usually does not need the separate word benim when the possessive ending already shows the meaning.

• boğazım already means my throat
• benim boğazım also means my throat, but it is more emphatic

So:

• Boğazım ağrıyor. = My throat hurts.
• Benim boğazım ağrıyor. = My throat hurts / It’s my throat that hurts (more emphasis)

In ordinary speech, boğazım is enough.

In Turkish, body parts often act like the subject of the verb ağrımak = to ache / to hurt.

So:

• Boğazım ağrıyor. literally = My throat is aching.
• natural English = My throat hurts.

Other examples:

• Başım ağrıyor. = My head hurts.
• Dizim ağrıyor. = My knee hurts.
• Karnım ağrıyor. = My stomach hurts.

So Turkish expresses this as the body part aches, not usually it hurts me.

Ağrıyor is in the present continuous form:

• ağrı-yor

But in Turkish, this form is often used not only for something happening right now, but also for:

• repeated situations
• habitual reactions
• general present situations

So here it can mean:

• my throat hurts when the tangerine juice is very cold
• my throat starts hurting whenever it’s very cold

It does not have to mean only at this exact moment.

Literally, çok soğuk means very cold.

• çok = very / a lot
• soğuk = cold

So:

• çok soğuk = very cold

In context, English might sometimes translate it more naturally as too cold, because the coldness causes a problem. But Turkish itself is just saying very cold.

If you specifically want too cold, Turkish often uses:

• fazla soğuk = too cold / excessively cold
• sometimes also çok soğuk can imply this in context

Turkish often puts the condition or background information first, and the main result later.

So the structure is:

• Mandalina suyu = tangerine juice
• çok soğuk olunca = when it is very cold
• boğazım ağrıyor = my throat hurts

Very literally:

When tangerine juice is very cold, my throat hurts.

This order is very natural in Turkish:
condition/cause → result

Usually it sounds like a general repeated reaction:

Whenever tangerine juice is very cold, my throat hurts.

That interpretation comes from:

• olunca = when/if
• ağrıyor = present continuous, often used for regular or recurring situations

If the speaker wanted to make it more clearly about one past event, Turkish would use a past form, for example:

• Mandalina suyu çok soğuk olunca boğazım ağrıdı. = My throat hurt when the tangerine juice was very cold.

Yes, that is possible, but the nuance is a bit different.

• ...çok soğuk olunca... = when it is very cold / when it gets very cold, often sounding like a situation that leads to a result
• ...çok soğuksa... = if it is very cold

So:

• Mandalina suyu çok soğuk olunca boğazım ağrıyor.
• Mandalina suyu çok soğuksa boğazım ağrıyor.

Both can work, but olunca often feels a little more like whenever that condition happens, this result follows.

Yes. Boğaz most commonly means throat, but in other contexts it can also mean a strait or narrow passage.

For example:

• Boğazım ağrıyor. = My throat hurts.
• İstanbul Boğazı = the Bosphorus

In your sentence, because of ağrıyor, it clearly means throat.