Bu işi beceremeyince bıktım.

Because iş is the direct object of becermek, and it is a specific/definite object.

• bu iş = this work / this task / this job
• bu işi = this work/task/job as a definite object

In Turkish, a definite direct object usually takes the accusative ending.

So:

• Bu iş zor. = This task is hard.
• Bu işi beceremedim. = I couldn’t manage this task.

With bu, the noun is already specific, so the accusative -i is expected here.

Here iş means something like task, piece of work, or thing to do.

Depending on context, iş can mean:

• work
• job
• task
• business / matter

In Bu işi beceremeyince bıktım, it most naturally means this task or this piece of work.

Becermek means to manage to do, to succeed at doing, to pull off, or to do successfully.

It is not exactly the same as yapmak:

• yapmak = to do / to make
• becermek = to manage to do well / to succeed in doing

So bu işi yapmak just means to do this task, but bu işi becermek suggests doing it successfully or competently.

That is why becerememek often feels like:

• not be able to do it properly
• fail to manage it
• not pull it off

A practical way to understand it is:

• becermek = to manage / succeed
• becerememek = to be unable to manage
• beceremeyince = when/since not being able to manage

So the whole form means something like:

• when I couldn’t manage it
• since I couldn’t manage it

For a learner, it is very useful to recognize -amayınca / -emeyince as a common pattern meaning:

• when one can’t ...
• since one couldn’t ...

The -y- is just a buffer consonant used between vowels.

Basically, -ince often means when or once. But in real sentences it can also feel like since / as / because, depending on context.

So beceremeyince bıktım can be understood as:

• When I couldn’t manage this task, I got fed up
• Since I couldn’t manage this task, I got fed up
• I got fed up because I couldn’t manage this task

In this sentence, the line between time and cause is blurry, and that is normal.

Because beceremeyince is not a full finite verb form like beceremedim. It is a subordinate/adverbial form.

Its time is usually understood from the context and from the main verb.

Here the main verb is:

• bıktım = I got fed up

Since that is in the past, English naturally translates the earlier clause as past too:

• when/since I couldn’t manage it

So Turkish does not always mark tense in subordinate clauses the same way English does.

Turkish often leaves subject pronouns out because the verb ending already shows the person.

• bıktım = I got fed up
• the -m tells you the subject is I

In beceremeyince, the subject is not separately marked, but it is understood from context, usually as the same subject as the main clause.

So the full sense is:

• When I couldn’t manage this task, I got fed up.

If needed, Turkish can make the subject explicit:

• Ben bu işi beceremeyince bıktım.

But usually ben is unnecessary.

No. Bıktım is stronger than I was bored.

It comes from bıkmak, which means:

• to get fed up
• to be sick and tired
• to grow weary of something

So bıktım means:

• I got fed up
• I became sick of it
• I got tired of it

Compare:

• sıkıldım = I got bored / I was bored
• bıktım = I got fed up / I’m sick and tired of it

In this sentence, the feeling is frustration, not simple boredom.

This is a very normal Turkish word order.

Turkish often puts:

1. the background/time/reason part first
2. the main verb at the end

So the structure is basically:

• Bu işi beceremeyince = when/since I couldn’t manage this task
• bıktım = I got fed up

Literal feel:

• Not being able to manage this task, I got fed up.

This is a natural, neutral order in Turkish.

Yes, absolutely.

That sentence means:

• I got fed up because I couldn’t manage this task.

Compared with beceremeyince:

• beceremeyince = more compact; can mean when/since
• beceremediğim için = more clearly because

So both are possible, but the nuance is a little different.

A natural English understanding would be something like:

• I got fed up because I couldn’t manage this task.
• I got tired of not being able to do this task.
• When I couldn’t manage this task, I got fed up.

The exact best translation depends on context, but the core idea is:

The speaker is frustrated and fed up because they are unable to handle the task successfully.

The ı in bıktım is the Turkish dotless i. It does not sound like English ee.

A rough guide:

• bıktım ≈ buhk-tuhm as a very loose approximation

But the Turkish ı is really its own sound, written /ɯ/ in linguistics. English does not have an exact equivalent.

So the main thing is:

• do not say beek-teem
• keep the vowels short and more central/back

The word is pronounced roughly as:

• bık-tım