Мотивація важлива.

In Ukrainian, the verb to be is usually omitted in the present tense.

So:

• Мотивація важлива. = Motivation is important.

This is completely normal and natural.
If you wanted other tenses, then forms of бути would appear:

• Мотивація була важлива. = Motivation was important.
• Мотивація буде важлива. = Motivation will be important.

Because it agrees with мотивація, which is a feminine singular noun.

In Ukrainian, adjectives must agree with the noun they describe in:

• gender
• number
• case

Here:

• мотивація = feminine singular
• важлива = feminine singular form of важливий (important)

Compare:

• важливий = masculine
• важлива = feminine
• важливе = neuter
• важливі = plural

Yes, that is a very strong clue. Many Ukrainian nouns ending in -я are feminine.

So мотивація is feminine, and that is why the adjective must also be feminine:

• мотивація важлива

That said, endings are a useful pattern, not an absolute rule for every noun in the language. But for this word, feminine is correct.

Both words are in the nominative singular.

• мотивація is the subject, so nominative makes sense.
• важлива is a predicate adjective and matches the subject in case, number, and gender.

So the structure is basically:

• [subject in nominative] + [adjective agreeing with it]

Yes. Ukrainian word order is more flexible than English, because endings carry a lot of grammatical information.

The most neutral version is:

• Мотивація важлива.

You may also see:

• Важлива мотивація.

But that usually feels more like important motivation as a noun phrase, not a full neutral statement.
So if you mean Motivation is important, the best basic sentence is:

• Мотивація важлива.

Yes, you can, but it is less simple and less everyday in this context.

• Мотивація важлива. = the most natural plain statement
• Мотивація є важливою. = more explicit, sometimes more formal, emphatic, or stylistically marked

Notice that with є and this structure, Ukrainian often uses the instrumental for the adjective:

• важливою instead of важлива

For a beginner, the shorter version is the one to remember first:

• Мотивація важлива.

The dictionary form is важливий.

That is the masculine singular nominative form, which is how Ukrainian adjectives are usually listed in dictionaries.

From that base, the adjective changes depending on the noun:

• важливий факт = an important fact
• важлива причина = an important reason
• важливе питання = an important question
• важливі речі = important things

So важлива is just the feminine form used here.

A helpful approximation is:

• Мотивація ≈ mo-ty-VA-tsi-ya
• важлива ≈ vazh-LY-va

The stress is:

• мотива́ція
• важли́ва

A few pronunciation notes:

• в is like v
• ж sounds like the s in measure
• ц sounds like ts
• я can sound like ya

Because важлива is an adjective agreeing with the noun мотивація.

• Мотивація важлива. = Motivation is important.

But важливо is a different form, often used in impersonal expressions such as:

• Це важливо. = This is important.
• Важливо знати це. = It is important to know this.

So:

• важлива = feminine adjective
• важливо = neuter form, often used like it is important or as an adverb

No. Ukrainian does not have articles like English a/an/the.

So Мотивація важлива can mean:

• Motivation is important
• sometimes, depending on context, The motivation is important

Usually the exact meaning comes from the situation, not from an article.

Yes. The plural is мотивації.

Examples:

• Мотивації важливі. = Motivations are important.

But in many contexts, мотивація is used as an uncountable abstract noun, much like English motivation.

So the singular sentence:

• Мотивація важлива.

is a very natural general statement.