Kemerim gevşemiş, bu yüzden yürürken pantolonum düşecek gibi oldu.

Kemer means belt. The ending -im is the 1st person singular possessive suffix, meaning my.

So:

• kemer = belt
• kemerim = my belt

The same thing happens later with pantolonum:

• pantolon = trousers / pants
• pantolonum = my trousers / my pants

Gevşemek means to loosen or to become loose.

So:

• gevşedi = it became loose / it loosened
• gevşemiş = it has apparently become loose / it had become loose / it turned out to be loose

The ending -miş often adds a nuance like:

• the speaker noticed the result afterward,
• the speaker is reporting it indirectly,
• or the speaker is focusing on the resulting state.

In this sentence, Kemerim gevşemiş sounds natural because it suggests something like:

• My belt had come loose
• My belt had apparently loosened
• It turned out my belt was loose

It fits well because the next part describes the consequence.

Bu yüzden means because of this, for this reason, or simply so.

It connects the first idea to the result:

• Kemerim gevşemiş = My belt had come loose.
• bu yüzden = because of that / so
• yürürken pantolonum düşecek gibi oldu = my pants almost fell while I was walking.

So bu yüzden introduces the consequence of the first clause.

It is a little different from çünkü:

• çünkü = because
• bu yüzden = therefore / so / for that reason

Here, bu yüzden is the better fit because the sentence goes from cause to result.

Yürürken means while walking.

It comes from:

• yürümek = to walk
• yürür = walks / is walking / walking (aorist-based form)
• -ken = while / when

So:

• yürürken = while walking

This is a very common structure in Turkish:

• yemek yerken = while eating
• konuşurken = while speaking
• eve giderken = while going home

In this sentence, yürürken tells you when the near-accident happened.

Yes, this is a common English-speaker question.

In Turkish, pantolon is usually treated as a singular noun, even though English often uses the plural pants or trousers.

So:

• pantolon = trousers / pants
• pantolonum = my trousers / my pants

Turkish does not have to match the English plural idea here. This is just a vocabulary difference between the two languages.

Very literally, it means something like:

it became as if it was going to fall

Breakdown:

• düşmek = to fall
• düşecek = will fall / is going to fall
• gibi = like / as if
• oldu = it became / it happened

Together, düşecek gibi oldu is a very natural Turkish way to say:

• it almost fell
• it seemed like it was about to fall
• it was on the verge of falling

So the literal pieces are a bit unusual in English, but the natural meaning is almost fell.

This is because the future here is future relative to that past moment, not future relative to now.

At the time the speaker was walking, the trousers seemed about to fall. From that past point of view, the falling was still in the immediate future.

So:

• düşecek gibi oldu does not mean they will fall later now
• it means they looked like they were going to fall at that moment

English does something similar:

• It looked like it was going to fall.

So the Turkish future marker -ecek / -acak can be used inside expressions about a past situation when something seemed imminent.

They only almost fell.

The key expression is düşecek gibi oldu. This suggests a near event, not a completed one.

If the trousers had really fallen, Turkish would say something more direct, such as:

• pantolonum düştü = my trousers fell

But here the meaning is:

• they nearly fell
• they were about to fall
• it seemed like they would fall

So the sentence describes a close call, not the actual fall.

In düşecek gibi oldu, oldu helps form the idea of it was as if... / it almost... / it came close to...

The pattern ... gibi olmak is common in Turkish. It can mean:

• to be like
• to seem as if
• to feel as though

In this sentence, oldu puts that whole impression into the past:

• düşecek gibi = as if it would fall
• düşecek gibi oldu = it was as if it would fall / it almost fell

So oldu is an important part of the expression, not just a simple standalone was.

Turkish word order is more flexible than English, but the verb usually comes at the end.

Here the structure is:

• yürürken = while walking
• pantolonum = my trousers
• düşecek gibi oldu = almost fell / seemed about to fall

So the sentence naturally builds toward the final verb expression.

A more literal word-by-word order would be:

• While walking, my trousers as-if-they-would-fall became

That sounds strange in English, but it is normal Turkish structure.

The Turkish sentence is perfectly natural because:

• time/context often comes earlier,
• the subject can come before the verb,
• the main predicate usually comes last.

Yes, that is a very good natural translation.

A few English versions that fit well are:

• My belt had loosened, so my pants almost fell while I was walking.
• My belt had come loose, so my pants nearly fell down while I was walking.
• My belt was loose, so it felt like my pants were about to fall while I was walking.

The exact English wording can vary a little, especially for düşecek gibi oldu, but almost fell or were about to fall both capture the meaning well.