Я завяжу синюю ленту на коробке и сделаю маленький бантик сверху.

Because both verbs are perfective: завязать and сделать. In Russian, perfective verbs often use the simple future to mean a single completed action in the future.

So:

• завяжу = I will tie
• сделаю = I will make

If you wanted to emphasize the process or repeated action, Russian would normally use imperfective verbs instead, such as буду завязывать or буду делать.

Their dictionary forms are:

• завязать → завяжу
• сделать → сделаю

Both are 1st person singular future: I will ...

This is why the sentence starts with Я and then uses these verb forms.

Russian can drop subject pronouns when the meaning is clear from the verb ending. So Завяжу синюю ленту... would also be possible.

But Я is often kept:

• for clarity
• for emphasis
• or simply because it sounds natural in context

So Я завяжу... means I will tie..., with I stated explicitly.

Because лента is the direct object of завяжу, so it goes into the accusative case.

• nominative: лента = ribbon
• accusative: ленту

Since лента is a feminine noun ending in -а, its accusative singular usually changes -а to -у.

So:

• синяя лента = a blue ribbon
• завяжу синюю ленту = I will tie a blue ribbon

Because the adjective has to agree with ленту in:

• gender
• number
• case

Here лента is:

• feminine
• singular
• accusative

So синий changes to синюю.

Compare:

• nominative: синяя лента
• accusative: синюю ленту

This is just adjective agreement.

That is the normal accusative singular feminine ending for adjectives like синий.

The pattern is:

• masculine: синий
• feminine nominative: синяя
• feminine accusative: синюю

So even though синюю may look unusual at first, it is a regular form.

Because here на коробке means on the box, describing a location.

With на, Russian often uses:

• prepositional case for location: на коробке = on the box
• accusative case for movement onto something: на коробку = onto the box

In this sentence, the ribbon is being tied on / around the box, so Russian treats the box as the place where the ribbon is.

Коробке is prepositional singular.

The noun is:

• dictionary form: коробка
• prepositional singular: на коробке

This happens because на is being used in a location sense: on the box.

Because бантик is the direct object of сделаю, and it is a masculine inanimate noun.

For masculine inanimate nouns, the accusative singular is the same as the nominative singular.

So:

• nominative: маленький бантик
• accusative: сделаю маленький бантик

That is why the form does not change here.

Бантик means a small bow, usually a decorative ribbon bow.

It is a diminutive form of бант.

So:

• бант = bow
• бантик = little bow / small bow

Using бантик sounds natural here because a ribbon bow on a box is typically small and decorative.

Сверху means on top, above, or at the top.

Here it tells you where the little bow will be placed: on top of the box or on the top part of the ribbon arrangement.

So:

• сделаю маленький бантик сверху = I’ll make a small bow on top

It is an adverb, not a noun or adjective.

Yes. Russian word order is fairly flexible.

The version in the sentence is a neutral, natural order:

• Я завяжу синюю ленту на коробке и сделаю маленький бантик сверху.

But you could move things around for emphasis, for example:

• Сверху я сделаю маленький бантик.
• На коробке я завяжу синюю ленту...

The basic meaning stays similar, but the emphasis changes. Russian word order often reflects focus and style, not just grammar.

Because Russian has no articles.

So:

• ленту can mean a ribbon or the ribbon
• коробке can mean the box or a box
• бантик can mean a bow or the bow

The exact meaning depends on context. English needs articles, but Russian does not.

A natural stress pattern is:

Я завяжу́ си́нюю ле́нту на коро́бке и сде́лаю ма́ленький ба́нтик све́рху.

A rough pronunciation guide:

• завяжу́ ≈ za-vya-ZHOO
• си́нюю ≈ SEE-nyu-yu
• ле́нту ≈ LYEN-too
• коро́бке ≈ ka-ROB-kye
• сде́лаю ≈ ZDYE-la-yu
• ба́нтик ≈ BAN-teek
• све́рху ≈ SVYER-khu

A common learner difficulty is синюю, because of the two vowel sounds at the end. It helps to say it slowly first: си-ню-ю.