Uzun süre bilgisayara bakınca boynum ağrıyor.

Because the verb bakmak (to look) usually takes the dative case in Turkish.

So:

• bilgisayar = computer
• bilgisayara = to/at the computer

With bakmak, Turkish says something like look at/to something, not just look something.

Examples:

• Televizyona bakıyorum. = I’m looking at the TV.
• Çocuğa baktı. = He/she looked at the child.

So bilgisayara bakmak means to look at the computer.

Bakınca comes from bakmak + -ınca / -ince, and here it means when, once, or whenever depending on context.

So:

• bakınca = when (someone) looks
• in this sentence, more naturally: when I look

In the full sentence, it gives the sense:

• When I look at the computer for a long time, my neck hurts.

Because the second part is a general statement, bakınca is understood as whenever/when in a habitual sense.

Yes, in this sentence that is how it is understood from context.

Turkish often leaves out subject pronouns when they are clear from the sentence. Here, the clue is boynum:

• boynum = my neck

Since the speaker says my neck hurts, we naturally understand the first part as when I look at the computer for a long time.

So Turkish does not need to repeat ben (I).

Because boynum means my neck.

Breakdown:

• boyun = neck
• boyn-um = my neck

The -um is the 1st person singular possessive suffix (my).

Also, the word changes slightly in form:

• base: boyun
• possessed form: boynum

This kind of small sound change is normal in Turkish.

Because Turkish usually expresses possession with a suffix, not a separate word like English does.

So instead of saying:

• my neck

Turkish often says:

• boynum

You can use benim boynum for extra emphasis, but it is usually unnecessary.

• Benim boynum ağrıyor. = My neck hurts. / My neck is what hurts.

In normal speech, boynum ağrıyor is enough.

Ağrıyor means hurts, is hurting, or aches, depending on context.

It comes from the verb ağrımak = to hurt / to ache.

So:

• Boynum ağrıyor. = My neck hurts. / My neck is hurting.

For body pain, ağrımak is very common:

• Başım ağrıyor. = My head hurts.
• Dişim ağrıyor. = My tooth hurts.

Yes, ağrıyor is in the present continuous form, but in Turkish this form is also often used for general or repeated situations, not only something happening right this second.

So this sentence can mean:

• My neck hurts when I look at the computer for a long time.
• My neck starts hurting if I look at the computer too long.

It sounds natural in Turkish even if the speaker means a habitual or repeated experience.

Uzun süre means for a long time.

Breakdown:

• uzun = long
• süre = duration / time / period

Together, they act like a time expression.

Turkish often uses time expressions without extra endings when they function adverbially:

• uzun süre bekledim = I waited for a long time
• iki gün çalıştım = I worked for two days

So uzun süre bilgisayara bakınca means when I look at the computer for a long time.

Yes. Turkish word order is flexible.

This sentence is natural as:

• Uzun süre bilgisayara bakınca boynum ağrıyor.

But you could also say:

• Bilgisayara uzun süre bakınca boynum ağrıyor.

Both mean essentially the same thing. The difference is mainly in emphasis:

• Uzun süre first emphasizes for a long time
• bilgisayara earlier can emphasize at the computer

The final verb ağrıyor usually stays at the end.

They are similar, but not always identical.

• bakınca = when/whenever I look
• baktığımda = when I look / when I looked / at the time that I look/looked

In many everyday sentences, they can both work:

• Uzun süre bilgisayara bakınca boynum ağrıyor.
• Uzun süre bilgisayara baktığımda boynum ağrıyor.

But bakınca often sounds a bit more like when/if/whenever that happens, while baktığımda can sound slightly more specific or structured.

For a learner, the important thing is:

• -ınca/-ince often gives a natural when/whenever meaning.

Yes. In Turkish, bakmak is commonly used for looking at a screen, object, or person.

So these are natural:

• Telefona bakmak = to look at the phone
• Bilgisayara bakmak = to look at the computer
• Ekrana bakmak = to look at the screen

So the sentence is using a very normal Turkish pattern.

Yes. That is a very natural interpretation too.

The -ınca/-ince form can sometimes overlap with English when and if, especially in cause-and-effect sentences.

So depending on context, this sentence can feel like:

• When I look at the computer for a long time, my neck hurts.
• If I look at the computer for a long time, my neck hurts.
• Whenever I look at the computer for a long time, my neck hurts.

In this example, whenever/when is probably the best overall sense.