Sedlo je příliš vysoké.

• sedlo = saddle / seat
• je = is
• příliš = too, excessively
• vysoké = high / tall

A very literal translation is Saddle is too high. In natural English, you add the or a from context: The saddle is too high.

Czech has no articles. It does not have separate words for a/an or the.

So:

• sedlo can mean a saddle, the saddle, or just saddle, depending on context.

If you want to be more explicit, Czech can use words like:

• to sedlo = that/the saddle
• jedno sedlo = one/a saddle in some contexts

But in a normal sentence, Czech usually leaves this to context.

Because vysoké has to agree with sedlo.

• sedlo is a neuter singular noun
• so the adjective also appears in the neuter singular form: vysoké

Compare:

• ten stůl je vysoký = the table is high/tall masculine
• ta skříň je vysoká = the wardrobe is tall feminine
• to sedlo je vysoké = the saddle is high neuter

English adjectives do not change form, but Czech adjectives do.

It is in the nominative singular.

Why?

• sedlo is the subject of the sentence
• the subject of a basic sentence is usually in the nominative

So:

• Sedlo = nominative singular subject
• je vysoké = predicate

Příliš means too in the sense of more than is acceptable or desirable.

So:

• příliš vysoké = too high

This is different from:

• velmi vysoké = very high
• hodně vysoké = quite/very high
• příliš vysoké = excessively high

So the sentence does not just mean the saddle is high. It means it is higher than it should be.

Yes. Moc is very common in everyday Czech.

So both are possible:

• Sedlo je příliš vysoké = a bit more neutral, careful, or formal
• Sedlo je moc vysoké = very common in spoken Czech

For many everyday situations, especially in speech, moc vysoké sounds more natural.

Yes, and in some contexts that may even sound more natural.

There is a useful difference:

• vysoké = high/tall as an adjective describing the thing
• vysoko = high/up high as an adverb describing position

So:

• Sedlo je příliš vysoké = the saddle is too high
• Sedlo je příliš vysoko = the saddle is positioned too high

If you are talking about adjusting a bicycle seat, many speakers would often prefer Sedlo je příliš vysoko or Sedlo je moc vysoko.

The sentence you were given is still grammatical and understandable.

In standard Czech, you normally do need je here.

• je is the 3rd person singular of být = to be
• it means is

So:

• Sedlo je příliš vysoké = correct
• Sedlo příliš vysoké = not a normal complete sentence in standard Czech

Unlike some languages, Czech normally keeps the present-tense form of to be in this kind of sentence.

Yes, Czech word order is fairly flexible, but the neutral order here is:

• Sedlo je příliš vysoké.

This is the most straightforward way to say it.

Other orders are possible, but they change emphasis:

• Příliš vysoké je sedlo. = marked, poetic, or contrastive
• Je sedlo příliš vysoké? = Is the saddle too high?

So for a learner, the best default is to keep:

• subject + je + příliš + adjective

A rough guide:

• Sedlo ≈ SED-lo
• je ≈ ye
• příliš ≈ roughly przhee-lish
• vysoké ≈ vi-SO-keh

A few important pronunciation points:

• Czech stress is usually on the first syllable of each word.
• í and é are long vowels, so you hold them a little longer.
• ř in příliš is a special Czech sound. It is one of the hardest Czech sounds for learners. You do not need to master it immediately to be understood.

So a simple learner-friendly rhythm is:

SED-lo ye PRZHEE-lish vi-SO-keh

Czech often uses vysoký / vysoko where English uses high.

So for physical height or position, Czech naturally says:

• je vysoké = is high
• je vysoko = is up too high / is positioned high

This is normal Czech usage. A native English speaker may want to translate more literally with something like raised too much, but Czech usually prefers the simple vysoké or vysoko.