Перед мостом будет опасный поворот, поэтому лучше ехать медленнее.

Because перед here means in front of / before, and after this preposition Russian normally uses the instrumental case.

• мост = bridge
• перед мостом = before the bridge / in front of the bridge

So мостом is simply the instrumental singular form of мост.

This is a very common pattern:

• перед домом = in front of the house
• перед машиной = in front of the car

In this sentence, перед мостом describes the location of the dangerous turn.

It can suggest either one in English, and in this sentence both ideas overlap a bit.

With places, перед + instrumental usually means in front of or just before reaching something:

• перед мостом будет опасный поворот = there will be a dangerous turn before the bridge / just in front of the bridge

So this is a spatial use, not a time expression like before dinner.

Russian leaves out to be only in the present tense, not in the future.

So:

• Здесь опасный поворот. = There is a dangerous turn here. / Here is a dangerous turn.
• Перед мостом будет опасный поворот. = There will be a dangerous turn before the bridge.

Here будет is the future form of быть and means there will be.

Because the thing that will be is опасный поворот — one dangerous turn.

The grammatical subject is поворот, which is:

• masculine
• singular
• nominative

So the verb is singular too:

• будет опасный поворот = there will be a dangerous turn

If it were plural, you would get:

• будут опасные повороты = there will be dangerous turns

Because опасный describes поворот, and both are in the nominative masculine singular.

• поворот = turn
• опасный = dangerous

Since поворот is masculine singular, the adjective must match it:

• опасный поворот

This is standard adjective-noun agreement in Russian.

Поворот means turn, especially in the road-driving sense here.

It can refer to:

• a bend in the road
• a turn you make while driving
• more generally, a turn/change in direction

In this sentence, because of the driving context, it means a dangerous bend/turn in the road.

Because поэтому means therefore / so / that’s why, and it introduces the result or conclusion of the first part.

So the sentence has two parts:

1. Перед мостом будет опасный поворот
2. поэтому лучше ехать медленнее

The comma separates the cause from the consequence:

• dangerous turn ahead → therefore it’s better to drive more slowly

This punctuation is normal in Russian.

Here лучше means it is better or better to.

In this sentence, it works as an impersonal predicative word, not as a normal adjective directly describing a noun.

• лучше ехать медленнее = it is better to drive more slowly

This is a very common Russian pattern:

• Лучше подождать. = It’s better to wait.
• Лучше не спешить. = It’s better not to hurry.

So лучше + infinitive is a useful structure to remember.

This is about the verb of motion.

• ехать = to go / drive in one direction, by vehicle
• ездить = to go / drive habitually, repeatedly, or in different directions
• поехать = perfective, to set off / go by vehicle

Here the sentence gives advice about how to drive at that point on the road, so ехать fits best:

• лучше ехать медленнее = it’s better to drive more slowly

It refers to the ongoing action of driving, not a repeated habit (ездить) and not the start of the trip (поехать).

Медленнее is the comparative form: more slowly / slower.

• медленно = slowly
• медленнее = more slowly / slower

Russian often uses the comparative in advice like this:

• лучше ехать медленнее = it’s better to drive more slowly

The idea is usually more slowly than you might otherwise drive.

You could say ехать медленно, but ехать медленнее sounds more natural in this kind of warning/advice context.

Here it functions as an adverb, because it describes how you should drive.

• ехать как? — медленнее
• drive how? — more slowly

It is the comparative form of the adverb медленно.

Yes. Russian word order is fairly flexible, although different orders change the emphasis.

The original sentence:

• Перед мостом будет опасный поворот, поэтому лучше ехать медленнее.

This emphasizes the location first: before the bridge.

You could also say:

• Опасный поворот будет перед мостом...

That sounds a little more like you are introducing the dangerous turn first, then saying where it is.

The original version is very natural, especially in warnings or road-related statements.

Not exactly. It is softer than a direct command.

• лучше ехать медленнее = it’s better to drive more slowly

That sounds like advice or a recommendation.

A direct command would be something like:

• Едьте медленнее! = Drive slower!
• Сбавьте скорость! = Slow down!

So the original sentence is informative and advisory, not sharply imperative.