Предоплата слишком высокая, чтобы я сразу согласилась на бронь.

This is the Russian equivalent of the English pattern too ... to ....

So:

• Предоплата слишком высокая = the prepayment is too high
• чтобы я сразу согласилась на бронь = for me to agree to the booking right away

Put together, the structure means:

• X is too Y for Z to happen

A very literal gloss would be:

• The prepayment is too high for me to agree to the booking immediately.

In Russian, чтобы introduces the action that is prevented by the degree of something.

Because чтобы introduces a subordinate clause.

Russian punctuation normally separates this kind of clause with a comma:

• Предоплата слишком высокая, чтобы...

This is standard and required here.

Because Russian often prefers a full clause with an explicit subject when the doer of the second action needs to be clear.

Here, the main clause is about предоплата (the prepayment), but the person doing the agreeing is я. Since the subjects are different, чтобы я согласилась is very natural and clear.

If you said чтобы сразу согласиться на бронь, it could still be understood in context, but it would be less explicit. The version with я makes it completely clear that I am the one who would be agreeing.

This is a very common Russian pattern.

After чтобы, Russian usually uses a verb form that looks like the past tense:

• чтобы я согласилась
• чтобы он пришёл
• чтобы мы сделали

But in this construction, it does not mean real past time. It expresses something hypothetical, desired, possible, or expected.

So чтобы я согласилась means:

• for me to agree
• so that I would agree

not that I agreed in the past.

Because the speaker is female.

Russian past-tense forms agree with gender in the singular:

• согласился = masculine
• согласилась = feminine
• согласилось = neuter
• согласились = plural

So if a man said this sentence, it would be:

• Предоплата слишком высокая, чтобы я сразу согласился на бронь.

Because it refers to a single completed act: agreeing.

Russian uses:

• соглашаться = imperfective, process/repeated action
• согласиться = perfective, one completed decision/action

Here the idea is to agree once, at that moment, to the booking. That is why согласилась is the natural choice.

If you used the imperfective, it would sound less natural here because the sentence is not about an ongoing process of agreeing.

Both are possible, but they sound a little different.

• высокая = full adjective form
• высока = short adjective form

In modern conversational Russian, the full form is very common in predicate position:

• Предоплата слишком высокая

The short form is also correct:

• Предоплата слишком высока, чтобы...

but it sounds a bit more formal or bookish.

So the sentence uses the more everyday option.

This comes from the pattern:

• согласиться на + accusative

It means to agree to, to accept, or to go along with something.

So:

• согласиться на бронь = agree to the booking / agree to make the booking

Here бронь is in the accusative case. Since бронь is an inanimate noun, its accusative form is the same as its nominative form:

• nominative: бронь
• accusative: бронь

Yes, бронь is a normal and very common word in everyday Russian, especially in travel, hotels, rentals, restaurants, and online booking contexts.

Compare:

• бронь = booking, reservation; short, conversational, very common
• бронирование = booking/reservation process; more formal or technical

So на бронь sounds natural in informal or business conversation.
A more formal version might use бронирование, but бронь is probably what many native speakers would actually say.

Сразу means right away, immediately, or on the spot.

It adds an important nuance: the speaker is saying the prepayment is too high for them to agree immediately. That leaves open the possibility that they might agree later, after thinking, negotiating, or getting more information.

Without сразу, the sentence would sound broader:

• Предоплата слишком высокая, чтобы я согласилась на бронь.

That means the prepayment is too high for me to agree to the booking at all.

With сразу, the meaning is softer and more specific.

Sometimes yes, but keeping it is clearer and more natural here.

Russian often drops pronouns when the subject is obvious, but in this sentence я helps because the main clause is about предоплата, while the subordinate clause is about me agreeing.

So:

• чтобы я сразу согласилась = very clear and natural

If you removed я, the sentence might still be understandable from context, but it would be less explicit.