Мне нравится этот оранжевый шарф, потому что он тёплый и очень яркий.

Because нравиться works differently from English to like.

Russian expresses this idea more like it is pleasing to me:

• мне = to me (dative case)
• нравится = is pleasing / appeals
• этот оранжевый шарф = the thing that is pleasing

So Мне нравится этот оранжевый шарф literally feels like:

To me, this orange scarf is pleasing.

That is why я is not used here.

Мне is the dative case of я.

You use the dative with нравиться to show the person who experiences the feeling:

• мне нравится = I like
• тебе нравится = you like
• ему нравится = he likes

So in this sentence, мне shows the person to whom the scarf is pleasing.

Because шарф is a masculine singular noun, and the demonstrative adjective must agree with it.

So:

• этот = masculine singular
• эта = feminine singular
• это = neuter singular

Since шарф is masculine, you need этот шарф.

Because adjectives in Russian must agree with the noun they describe in:

• gender
• number
• case

Here, шарф is:

• masculine
• singular
• nominative

So the adjective also takes the masculine singular nominative form:

• оранжевый шарф

If the noun changed, the adjective would change too:

• оранжевая шапка = orange hat
• оранжевое пальто = orange coat

It is in the nominative case.

With нравится, the thing being liked is usually in the nominative, because grammatically it acts like the subject of the verb:

• Мне нравится шарф.
• literally: The scarf is pleasing to me.

So:

• мне = dative
• этот оранжевый шарф = nominative

Because the subject is singular:

• этот оранжевый шарф = one scarf

So the verb is singular:

• нравится = singular

If there were several scarves, you would use нравятся:

• Мне нравятся эти шарфы. = I like these scarves.

Он means he/it, and here it means it, referring back to шарф.

Russian nouns have grammatical gender, and шарф is masculine, so the pronoun must also be masculine:

• шарф → он

In English, we say it for objects, but in Russian you choose the pronoun based on grammatical gender.

They are predicate adjectives describing он / шарф, so they must agree with that masculine singular noun.

That is why you get:

• он тёплый
• он яркий

Both adjectives are in the masculine singular form.

If the noun were feminine, the forms would change:

• Она тёплая и яркая.

Потому что means because.

It introduces the reason:

• Мне нравится этот оранжевый шарф = I like this orange scarf
• потому что он тёплый и очень яркий = because it is warm and very bright

Unlike in some languages, Russian does not force the verb to the end after because. The word order here is normal and natural.

Because потому что introduces a subordinate clause, and in Russian that clause is separated by a comma.

So this is standard punctuation:

Мне нравится этот оранжевый шарф, потому что он тёплый и очень яркий.

That comma is required in normal writing.

Очень means very.

It modifies яркий:

• яркий = bright
• очень яркий = very bright

So the sentence says the scarf is:

• тёплый = warm
• очень яркий = very bright

It only strengthens яркий here, not тёплый.

Because ё is a separate letter in Russian and it shows the sound yo.

So:

• тёплый is pronounced roughly TYOP-lyy

A useful thing to remember: ё is always stressed.

In many printed texts, ё is sometimes replaced by е, so you may also see теплый, but the correct pronunciation is still тёплый.

Yes, but it means something a bit stronger.

• Мне нравится этот оранжевый шарф = I like this orange scarf
• Я люблю этот оранжевый шарф = I love this orange scarf

For ordinary preferences, нравится is usually the more natural choice. Люблю sounds stronger and more emotional.

Yes, Russian word order is more flexible than English, but this sentence uses the most neutral, natural order.

Standard order:

Мне нравится этот оранжевый шарф, потому что он тёплый и очень яркий.

You can move things around for emphasis, but for a learner this version is the safest and most natural.