Если мы выйдем пораньше, мы успеем на последний автобус.

Because Russian often uses the simple future of perfective verbs for actions that will be completed in the future.

• выйти = to go out / leave (perfective)
• успеть = to manage to be in time / make it (perfective)

So:

• мы выйдем = we will leave
• мы успеем = we will make it / be in time

In English, future meaning is often shown with will, but in Russian, perfective verbs form the future with endings that look like present-tense endings:

• выйду, выйдешь, выйдет...
• успею, успеешь, успеет...

So even though they look a bit like present forms, they actually mean future here.

That is a very common question. Russian and English handle this differently.

In Russian, with a real future condition, it is normal to use future forms in both clauses:

• Если мы выйдем пораньше, мы успеем...

Literally, this is closer to:

• If we leave earlier, we will make it...

But grammatically, Russian is perfectly happy to use future in the если clause.

So English avoids will after if, but Russian does not avoid the future there.

пораньше means a bit earlier, somewhat earlier, or rather early.

It is related to раньше = earlier.

Compare:

• раньше = earlier
• пораньше = a little earlier / somewhat earlier

In this sentence, пораньше suggests that leaving just a bit earlier would be enough.

So:

• Если мы выйдем раньше... = If we leave earlier...
• Если мы выйдем пораньше... = If we leave a bit earlier...

The prefix по- often softens the meaning and can make it sound more natural or conversational.

Yes, both can often translate as leave, but they are not always interchangeable.

• выйти literally means to go out, to exit
• уйти means to go away, to depart

In many contexts, either could work, depending on what you want to emphasize.

• выйдем can suggest physically going out from a place
• уйдём can sound more like departing in general

In this sentence, выйдем пораньше is very natural if the idea is leave the house / leave the building earlier.

So the speaker is probably thinking in terms of going out earlier, not just abstractly departing.

Because Russian uses успеть на with things like transport, events, lessons, trains, planes, and so on.

So:

• успеть на автобус = to catch the bus / be in time for the bus
• успеть на поезд = to catch the train
• успеть на урок = to make it to class on time
• успеть на встречу = to make it to the meeting on time

The noun after на is in the accusative case:

• на последний автобус

This whole phrase means something like in time for the last bus or to catch the last bus.

It is accusative because it follows the preposition на in the expression успеть на что?

• на автобус → accusative

For an inanimate masculine noun, the accusative singular is usually the same as the nominative singular.

So:

• nominative: последний автобус
• accusative: последний автобус

That is why the form does not visibly change here.

If the noun were feminine or plural, you might see a clearer change.

Russian often omits subject pronouns when the verb ending already makes the subject clear.

So this sentence could also be:

• Если выйдем пораньше, успеем на последний автобус.

That sounds natural in many contexts.

Why keep мы then?

• for emphasis
• for clarity
• for rhythm
• because spoken Russian often includes pronouns even when they are not strictly necessary

So both versions are possible:

• Если мы выйдем пораньше, мы успеем...
• Если выйдем пораньше, успеем...

The version with мы is slightly more explicit.

Because Russian normally separates the two parts of a complex sentence with a comma, including sentences with если.

So:

• Если мы выйдем пораньше, мы успеем на последний автобус.

The first clause is the condition:

• Если мы выйдем пораньше

The second clause is the result:

• мы успеем на последний автобус

Russian punctuation is stricter here than English learners sometimes expect: the comma is required.

Yes. Russian word order is flexible, though not random.

A very common alternative is:

• Мы успеем на последний автобус, если выйдем пораньше.

This means the same thing: We’ll catch the last bus if we leave earlier.

You can also omit pronouns:

• Успеем на последний автобус, если выйдем пораньше.

Changing the order can shift the focus slightly:

• starting with Если... emphasizes the condition first
• starting with Мы успеем... emphasizes the result first

Both are natural.

Both main verbs are perfective:

• выйти → выйдем
• успеть → успеем

Aspect matters because the sentence is about single completed future actions:

• leaving once
• managing to catch the bus successfully

Perfective verbs are the normal choice when you mean a future action as a complete event.

If you used imperfective verbs instead, the meaning would change or sound unnatural here.

For example:

• выходить is imperfective and usually refers to repeated action, process, or habitual action
• успевать is imperfective and often means habitually being in time or being in the process of managing

This sentence is about one specific future situation, so perfective is the right choice.

Not in this sentence as it stands.

• Если = if for a real or possible condition
• если бы = if for an unreal / hypothetical condition, usually like if we left earlier, we would...

Your sentence is about a real possibility in the future:

• Если мы выйдем пораньше, мы успеем...
• If we leave a bit earlier, we’ll catch...

If you used если бы, the sentence would become more hypothetical and would require different verb forms, usually with бы in the main clause too:

• Если бы мы вышли пораньше, мы бы успели на последний автобус.
• If we had left earlier / If we left earlier, we would have caught the last bus.

So the original sentence uses если because it is a realistic future plan, not an unreal situation.

In this context, it usually means the last bus of the day.

That is the most natural interpretation because catching the last bus is a very common real-life situation.

So the sentence strongly suggests:

• if we leave a little earlier, we will still be in time for the final bus service

Without context, последний can simply mean last, but here it almost certainly means the final available bus.

The original sentence is already very natural and neutral.

A few conversational variants:

• Если выйдем пораньше, успеем на последний автобус.
• Если чуть пораньше выйдем, успеем на последний автобус.

A slightly more explicit version:

• Если мы выйдем немного раньше, мы успеем на последний автобус.

Differences:

• пораньше sounds natural and conversational
• немного раньше is a bit more literal: a little earlier
• omitting мы sounds more casual and fluid in everyday speech

So the given sentence is a very good standard version.