péngyou duì wǒ shuō jiāyóu.

对 marks the person that the speech is directed toward.

So the pattern is:

A 对 B 说 + spoken content

which means:

A says ... to B

In this sentence:

• 朋友 = the speaker
• 我 = the listener
• 说 = to say
• 加油 = what was said

So 对我说 means say to me.

The structure is:

朋友 + 对我 + 说 + 加油

A natural way to understand it is:

• 朋友 = friend
• 对我 = to me
• 说 = said
• 加油 = the words spoken

So the overall pattern is:

[speaker] + 对/跟 + [listener] + 说 + [content]

English often puts the listener after say:
A friend said to me...

Chinese commonly puts that listener phrase before 说:
朋友对我说...

Here 加油 is an encouraging expression.

Its literal meaning is add oil, but that is not how it is understood in normal speech. In real use, it can mean things like:

• Come on!
• Keep it up!
• You can do it!
• Go for it!

The best English translation depends on the situation.

So in this sentence, the friend is encouraging the speaker.

In normal writing, yes, punctuation usually makes it clearer.

Common written versions would be:

• 朋友对我说：加油！
• 朋友对我说，加油！

The version without punctuation, 朋友对我说加油。, is understandable, especially in beginner materials, but in natural writing people often add a colon, comma, or quotation-style punctuation to show that 加油 is the spoken content.

In speech, intonation and pauses make this clear, so punctuation is not an issue.

By itself, 朋友 can be interpreted from context.

Chinese does not use articles like a or the the way English does, so 朋友 could mean:

• a friend
• my friend
• the friend
• sometimes even friends, depending on context

In this sentence, most learners would probably understand it as a friend or my friend.

If you want to say my friend explicitly, you can say:

我的朋友对我说加油。

If you want to show plural clearly, you might use context or say:

朋友们

But here, singular is the most natural reading.

Yes. 跟我说 is very common and natural.

So this also works:

朋友跟我说加油。

The difference is small:

• 对我说 can feel a bit more directional or slightly more formal/written
• 跟我说 is very common in everyday speech

Both are correct here.

Mandarin does not mark tense the same way English does.

This sentence can be understood as past, present, or even habitual depending on context. Very often, context tells you the time.

So 朋友对我说加油。 could mean something like:

• a friend said 加油 to me
• a friend says 加油 to me
• a friend tells me 加油

If you want to make a past event clearer, you could add a time word, such as:

昨天朋友对我说：加油！

With a short spoken expression like 加油, native speakers also often say:

朋友对我说了一句加油。

That clearly shows one completed utterance.

Both are understandable, but they feel a little different.

说加油 is shorter and simpler. It is common in teaching examples because it shows the structure clearly.

说了一句加油 is more explicit and often sounds more natural when you are reporting a short expression someone said.

For example:

• 朋友对我说加油。
• 朋友对我说了一句加油。

The second version highlights that 加油 was one specific utterance.

In writing, another very natural version is:

朋友对我说：加油！

In this sentence, because 加油 comes after 说, it is most naturally understood as the actual words spoken.

So the idea is:

My friend said to me: 加油

If you want to say that the friend was cheering you on as an action, not necessarily quoting the exact words, Chinese often uses a different pattern, such as:

• 朋友给我加油。
• 朋友为我加油。

These mean that the friend was encouraging or cheering for you.

So:

• 对我说加油 = said 加油 to me
• 给我加油 / 为我加油 = cheered me on

Sometimes yes, if the listener is obvious from context.

For example, in conversation, someone might just say:

朋友说加油。

But that is less specific. It could mean:

• a friend said 加油
• a friend said that someone should keep going

Including 我 makes the target clear:

朋友对我说加油。

So the original sentence is clearer for learners because it shows exactly who received the words.