Der Sattel ist zu hoch.

Because Sattel is a masculine noun in German. Its dictionary form is der Sattel.

German nouns have grammatical gender:

• der = masculine
• die = feminine
• das = neuter

So if you want to say the saddle, you say der Sattel.

Sattel usually means saddle. Depending on context, it can refer to:

• a horse saddle
• a bicycle seat/saddle

In a sentence like Der Sattel ist zu hoch, it is very often understood as a bike saddle or seat height context.

In a normal German main clause, the finite verb usually comes in position 2.

So in:

• Der Sattel = subject
• ist = finite verb
• zu hoch = complement

This follows the standard German word order pattern:

• Subject + verb + rest

Zu hoch means too high, not just very high.

Important difference:

• hoch = high / tall
• sehr hoch = very high
• zu hoch = too high

So zu here shows that the height is more than desired or appropriate.

Here, zu is an adverb meaning too.

Examples:

• zu hoch = too high
• zu groß = too big
• zu teuer = too expensive

This is different from other uses of zu, such as:

• zu Hause = at home
• zur Schule = to school
• zu + infinitive = e.g. Ich versuche zu lernen

So in this sentence, zu simply means too.

Because hoch is being used here as a predicate adjective, after the verb sein.

In German:

• attributive adjectives (before a noun) take endings
  
  • der hohe Sattel
• predicate adjectives (after sein, werden, bleiben, etc.) do not take endings
  
  • Der Sattel ist hoch
  • Der Sattel ist zu hoch

So hoch stays unchanged here.

Yes, but it means something different.

• Der Sattel ist hoch. = The saddle is high.
• Der Sattel ist zu hoch. = The saddle is too high.

The version with zu adds the idea that the height is a problem or not suitable.

Yes. Hoch is the normal adjective for something being high.

In bike or seat adjustment contexts, Germans often use:

• zu hoch = too high
• zu niedrig = too low

So if the saddle needs to be lowered, zu hoch is exactly the natural phrase.

The most natural negative version is:

• Der Sattel ist nicht zu hoch. = The saddle is not too high.

If you said:

• Der Sattel ist nicht hoch.

that means:

• The saddle is not high.

So the position of nicht changes what is being negated:

• nicht zu hoch = not too high
• nicht hoch = not high

A simple yes/no question is:

• Ist der Sattel zu hoch? = Is the saddle too high?

German forms this kind of question by putting the verb first:

• statement: Der Sattel ist zu hoch.
• question: Ist der Sattel zu hoch?

Sattel is pronounced approximately like ZAH-tel.

A few notes:

• S at the beginning before a vowel is usually pronounced like z in German
• tt makes the preceding vowel short
• the a is short, not like the long vowel in English father

So it sounds roughly like:

• ZAH-tel with a short a

Yes. Since Sattel is masculine, the pronoun is er.

So:

• Der Sattel ist zu hoch.
• Er ist zu hoch.

Here er means it, because German pronouns follow grammatical gender, not natural gender.

This pattern is very common:

• Der Tisch ist zu hoch. = The table is too high.
• Der Stuhl ist zu niedrig. = The chair is too low.
• Das Fahrrad ist zu groß. = The bicycle is too big.
• Die Tasche ist zu schwer. = The bag is too heavy.

The pattern is:

• [noun] + ist + zu + adjective

It is a very useful structure for describing problems or making adjustments.