syuumatu ni tomodati to issyo ni hanabi wo mi ni ikimasu.

A natural reading is:

しゅうまつ に ともだち と いっしょ に はなび を み に いきます。

Word by word:

• 週末 = しゅうまつ = weekend
• 友達 = ともだち = friend / friends
• 一緒 = いっしょ = together
• 花火 = はなび = fireworks
• 見 = the stem of 見る（みる） = to see / watch
• 行きます = いきます = go

So the full sentence is read:

しゅうまつ に ともだち と いっしょ に はなび を み に いきます。

Each に is doing a different job.

1. 週末に
   Here に marks the time: at/on the weekend.

2. 一緒に
   Here に turns 一緒 into an adverb-like expression meaning together.

3. 見に行きます
   Here に is part of the pattern verb stem + に行く, which means go to do something.

So even though the same particle appears several times, the function changes depending on where it appears.

In this sentence, と means with.

• 友達と = with a friend / with friends

This と is used to show the person you do something together with.

So:

• 友達と一緒に = together with a friend / friends

Yes, a little—but it is still very natural.

• 友達と already means with a friend
• 一緒に adds the feeling of together

So 友達と一緒に is like saying:

• with my friend, together
• or more naturally in English, just together with a friend

Japanese often uses both for emphasis or natural flow. You could say just 友達と in some cases, but 友達と一緒に sounds very normal.

This is the grammar pattern:

verb stem + に行く = go to do ...

For 見る, the stem is 見（み）.

So:

• 見に行きます = go to see/watch

Other examples:

• 食べに行きます = go to eat
• 買いに行きます = go to buy
• 遊びに行きます = go to hang out / go have fun

So 花火を見に行きます literally means go to see fireworks.

Because 花火 is the direct object of 見る.

• 花火を見る = watch fireworks

Even though 見 is only appearing as a stem in 見に行きます, it still keeps its object:

• 花火を見に行きます = go to watch fireworks

So を marks the thing being seen.

一緒（いっしょ） means together.

In this sentence it appears as 一緒に, which works like an adverb:

• 友達と一緒に = together with a friend

By itself, 一緒 can also mean the same or together, depending on context. But here it clearly means together.

Often, yes.

Many time expressions in Japanese can appear with or without に, depending on the word and the speaker’s style. With 週末, both are heard:

• 週末に花火を見に行きます
• 週末花火を見に行きます

That said, 週末に is very clear and very common for learners to use. It sounds completely natural.

Japanese -ます forms are often called non-past rather than strictly present.

So 行きます can mean:

• go (habitual / general)
• will go (future)

In this sentence, because of 週末に and the context, it clearly means the future:

• I will go see fireworks this weekend.

Japanese usually does not need a separate future tense form the way English does.

The subject is omitted, which is extremely common in Japanese.

The sentence does not explicitly say I, we, or someone else. In real conversation, the subject is often understood from context.

So depending on the situation, it could mean:

• I’m going to see fireworks this weekend with a friend.
• We’re going to see fireworks this weekend with friends.

In a textbook, it is often translated as I because that is the most neutral guess when no subject is stated.

It can mean friend or friends.

Japanese nouns usually do not change form for singular vs. plural the way English nouns do.

So:

• 友達 = friend / friends

You understand the number from context. If the speaker wants to be more specific, they can add something else, but by itself 友達 is flexible.

花火 usually refers to fireworks as a general event or display.

Even though the word is literally made from:

• 花 = flower
• 火 = fire

the actual meaning is fireworks.

Like many Japanese nouns, it does not need a special plural form. In English we usually translate it as fireworks, not a firework, unless context makes it singular.

The structure is:

[time] + [person you’re with] + [manner] + [object] + [purpose] + [main verb]

In this sentence:

• 週末に = time
• 友達と = with a friend
• 一緒に = together
• 花火を = object
• 見に = purpose
• 行きます = main verb

So the sentence is built very logically, with the main verb 行きます coming at the end, as is normal in Japanese.

Yes, to some extent. Japanese word order is more flexible than English, as long as the particles make the relationships clear.

For example, these are still understandable:

• 週末に花火を友達と一緒に見に行きます。
• 友達と一緒に週末に花火を見に行きます。

However, the original order sounds very natural and easy to follow:

• 週末に友達と一緒に花火を見に行きます。

So while Japanese allows some movement, not every order sounds equally natural.

Yes, but the meaning changes.

• 花火を見ます = watch fireworks
• 花火を見に行きます = go to watch fireworks

The second sentence emphasizes the going as well as the watching. It implies movement to another place for that purpose.

So if you want to express going somewhere in order to watch fireworks, 見に行きます is the correct choice.