Один шнурок был мокрым и слишком длинным, и мне пришлось остановиться у скамейки.

Yes. Один is the number one, and here it literally means one shoelace.

In this sentence, it naturally implies one of the shoelaces was wet and too long. Russian often says this very directly:

• Один шнурок... = One shoelace...

Because shoes normally have more than one lace, the meaning one of them is understood from context.

Шнурок literally means a lace, string, or cord, depending on context. In this sentence, it clearly means shoelace.

So:

• шнурок = lace / cord / shoelace
• here: shoelace

Russian often relies on context instead of adding an extra word like shoe-.

This is a very common learner question.

After быть in the past or future, Russian can use the predicate adjective in either:

• nominative: мокрый, длинный
• instrumental: мокрым, длинным

So both are possible:

• шнурок был мокрый
• шнурок был мокрым

In modern Russian, the instrumental after был is very common and often sounds especially natural in descriptive statements like this.

So:

• был мокрым
• был длинным

are just predicate adjectives in the instrumental case.

They are instrumental singular masculine forms.

The noun they describe is:

• шнурок — masculine singular

So the adjectives match it:

• мокрый → мокрым
• длинный → длинным

This happens because they are being used after был as predicate adjectives in the instrumental.

Слишком means too, as in more than is desirable.

So:

• слишком длинным = too long

It usually goes before the adjective or adverb it modifies:

• слишком длинный = too long
• слишком быстро = too quickly

Here it modifies длинным.

Пришлось is the past tense of the verb прийтись in an impersonal construction.

The expression:

• мне пришлось остановиться

means:

• I had to stop
• more literally: it fell to me to stop

This is a very common Russian way to express necessity caused by circumstances.

Compare:

• Мне пришлось уйти. = I had to leave.
• Нам пришлось ждать. = We had to wait.

Because this construction uses the dative case, not the nominative subject.

So:

• мне = to me / for me
• тебе = to you
• ему = to him
• нам = to us

Russian says:

• Мне пришлось остановиться.

not

• Я пришлось остановиться. ❌

This is because пришлось here is impersonal. The person experiencing the necessity goes in the dative.

Both can mean I had to stop, but the nuance is different.

Мне пришлось остановиться

This usually means:

• circumstances forced it
• it became necessary
• I ended up having to stop

Я должен был остановиться

This usually suggests:

• obligation
• duty
• something I was supposed to do

In this shoelace sentence, мне пришлось остановиться is more natural because the need to stop comes from the situation, not from a rule or moral duty.

Because остановиться is perfective, and here the sentence refers to a single completed action: stopping.

• остановиться = to stop, to come to a stop once
• останавливаться = to stop repeatedly / to be stopping / the imperfective version

Since the sentence means that the speaker had to stop at that moment, the perfective infinitive is the normal choice:

• мне пришлось остановиться

У скамейки means by the bench, near the bench, or next to the bench.

The preposition у means by / near / at, and it requires the genitive case.

So:

• скамейка = bench
• у скамейки = by the bench

If you used скамейку, that would be accusative, and it would not fit with у.

It is genitive singular.

The base form is:

• скамейка = bench

After у, it becomes:

• у скамейки = by the bench

This is because у takes the genitive case.

Yes. Both are possible.

• у скамейки = by the bench / right by the bench
• около скамейки = near the bench

Very often, у sounds a bit more like right next to something, while около can sound a bit more general, but in many contexts they are close in meaning.

In the present tense, Russian usually omits to be:

• Шнурок мокрый. = The shoelace is wet.

But in the past tense, Russian uses forms of быть:

• Шнурок был мокрым. = The shoelace was wet.

So был is required here because the sentence is in the past.

That и simply means and and connects the two parts of the sentence:

1. Один шнурок был мокрым и слишком длинным
2. мне пришлось остановиться у скамейки

So the whole sentence is:

• One shoelace was wet and too long, and I had to stop by a bench.

There is also another и inside the first part:

• мокрым и слишком длинным = wet and too long

So the sentence uses и twice for two different links:

• between two adjectives
• between two clauses

Russian word order is fairly flexible, but this version is neutral and natural.

Original:

• Один шнурок был мокрым и слишком длинным, и мне пришлось остановиться у скамейки.

You could change the order for emphasis, for example:

• Мне пришлось остановиться у скамейки, потому что один шнурок был мокрым и слишком длинным.

But the original order is straightforward and sounds normal.

Yes, it is grammatical and understandable.

It may sound a little specifically descriptive, because in real life a shoelace being both wet and too long is quite detailed, but as a Russian sentence it is perfectly natural.

A native speaker would understand it immediately as a reason the speaker needed to stop.