Im wyższy jest grzbiet, tym trudniejsze jest podejście.

It is the Polish equivalent of the English pattern the ..., the ... in comparisons:

• Im wyższy jest grzbiet... = The higher the ridge...
• tym trudniejsze jest podejście = ...the harder the ascent

So the whole structure expresses a relationship: when one thing increases, another changes accordingly.

A useful pattern to remember is:

• Im + comparative ..., tym + comparative ...

For example:

• Im później, tym gorzej. = The later, the worse.

In this construction, tym is the normal fixed partner of im. Learners should mostly treat im ..., tym ... as one set expression.

Historically, tym is related to forms of ten/to, but in modern Polish the important thing is simply:

• im introduces the first comparison
• tym introduces the second comparison

So when you want to say the more..., the more... or the higher..., the harder..., Polish normally uses im ..., tym ....

Because Polish adjectives must agree with the nouns they describe.

Here:

• grzbiet is masculine singular, so the comparative adjective is wyższy
• podejście is neuter singular, so the comparative adjective is trudniejsze

That is why the endings are different.

You can think of it like this:

• wyższy grzbiet = a higher ridge
• trudniejsze podejście = a harder ascent

Even in the comparative, Polish adjectives still change for gender, number, and case.

Yes. Both are comparatives:

• wysoki → wyższy = high → higher
• trudny → trudniejszy / trudniejsze = difficult → more difficult / harder

In English, harder never changes form depending on the noun. In Polish, the comparative still has to match the noun:

• wyższy for masculine singular
• trudniejsze for neuter singular

So trudniejsze is still the same comparative adjective as trudniejszy; it is just a different agreeing form.

They are both in the nominative.

That is because each part of the sentence is built around jest (is), and the nouns are the subjects:

• grzbiet jest wyższy = the ridge is higher
• podejście jest trudniejsze = the ascent is harder

Also, predicate adjectives after być usually appear in the nominative in Polish:

• On jest wysoki. = He is tall.

So in this sentence, both the noun and the agreeing adjective are in nominative forms.

Because Polish word order is flexible, and in this construction the comparative adjective is very often placed right after im.

So:

• Im wyższy jest grzbiet, tym trudniejsze jest podejście.

sounds natural and elegant.

You could also say:

• Im grzbiet jest wyższy, tym podejście jest trudniejsze.

That is grammatical, but it sounds heavier and less idiomatic. The version with the comparative immediately after im is usually the most natural.

It is repeated because each half is a complete clause:

• wyższy jest grzbiet
• trudniejsze jest podejście

Polish often allows a shorter version without jest, especially in compact or proverb-like statements:

• Im wyższy grzbiet, tym trudniejsze podejście.

That version is also correct and quite natural.

So:

• with jest = fuller, more explicit
• without jest = shorter, more compressed

Yes, you can. It is grammatical and fully understandable.

However, Polish usually prefers the more compact pattern with the comparative placed early:

• Im wyższy jest grzbiet, tym trudniejsze jest podejście.

or even:

• Im wyższy grzbiet, tym trudniejsze podejście.

So your version is not wrong, but it is less streamlined than the original.

Because Polish has no articles. There is no direct equivalent of English a/an/the used in ordinary noun phrases.

So:

• grzbiet can mean a ridge or the ridge
• podejście can mean an ascent or the ascent

The exact meaning depends on context.

Also, in the English pattern the higher..., the harder..., the word the is not really functioning like a normal article. It is part of a special comparative structure. Polish expresses that structure with im ..., tym ..., not with articles.

Polish has two main ways to make comparatives:

1. Synthetic comparatives: one changed adjective form

   • wysoki → wyższy
   • trudny → trudniejszy

2. Analytical comparatives with bardziej

   • bardziej interesujący = more interesting

For common adjectives like wysoki and trudny, the synthetic forms are normal and preferred. So:

• wyższy is better than bardziej wysoki
• trudniejszy is better than bardziej trudny

That is why the sentence uses wyższy and trudniejsze, not bardziej forms.

No. It is very common with adjectives, but it can also be used more broadly.

Examples:

• Im więcej czytam, tym więcej rozumiem.
  The more I read, the more I understand.

• Im szybciej pojedziemy, tym wcześniej dojedziemy.
  The faster we go, the earlier we’ll arrive.

• Im trudniejsze zadanie, tym większa satysfakcja.
  The more difficult the task, the greater the satisfaction.

So the sentence you were given is one example of a very productive Polish pattern.