Starttaket og fottaket er lave.

Because Norwegian usually writes compound nouns as a single word.

So:

• starttaket = start
  • taket
• fottaket = fot
  • taket

English often uses separate words, but Norwegian prefers compounds much more often.

Here, -et is the definite ending for a singular neuter noun.

That means:

• et starttak = a starting hold
• starttaket = the starting hold
• et fottak = a foothold
• fottaket = the foothold

So Norwegian often puts the at the end of the noun instead of using a separate word before it.

You can tell from the forms et starttak and et fottak. In Norwegian, nouns can be common gender or neuter, and these take the neuter article et.

Their definite singular forms therefore end in -et:

• et starttak → starttaket
• et fottak → fottaket

If they were common gender nouns, you would usually see en and the definite ending -en instead.

Because the sentence has two things joined by og: starttaket og fottaket.

Even though each noun is singular by itself, together they make a plural subject. In Norwegian, predicate adjectives agree with the subject, so the adjective must be plural:

• Starttaket er lavt. = one neuter thing is low
• Fottaket er lavt. = one neuter thing is low
• Starttaket og fottaket er lave. = two things are low

So lavt would be right for one neuter noun, but lave is right for two.

The adjective changes depending on gender and number:

• lav = singular common gender
• lavt = singular neuter
• lave = plural

So you can compare:

• en vegg er lav = a wall is low
• et tak er lavt = a ceiling is low
• veggene er lave = the walls are low

In your sentence, lave is used because the subject is plural overall.

Because Norwegian does not change the present-tense form of å være the way English does.

English has:

• is
• are

Norwegian uses er for both:

• Starttaket er lavt.
• Starttakene er lave.
• Starttaket og fottaket er lave.

So er works with both singular and plural subjects.

Because each noun refers to one specific item:

• one starttak
• one fottak

The sentence is not talking about several starting holds or several footholds. It is talking about one of each, connected by og.

If there were several of each, you would use plural nouns, for example:

• starttakene og fottakene

Because in Norwegian, the definite article is often attached to the noun itself.

So instead of a separate word like English the, Norwegian often uses:

• -en
• -et
• -a

That is why you have starttaket and fottaket, not a separate the before them.

A useful extra point: if you add an adjective before a definite noun, Bokmål often uses both a separate article and the ending:

• det lave starttaket = the low starting hold

But in your sentence, the adjective comes after er, so you just see the definite noun form by itself.

Only because it is the first word of the sentence.

Norwegian does not capitalize all nouns the way German does. If the noun appeared in the middle of the sentence, it would normally be lowercase:

• Fottaket og starttaket er lave.

So the capital S here is just normal sentence capitalization.