Learn Russian: Дорога всегда оказывается длиннее, чем думаешь. - The road always turns out longer than you think.

In Russian, you can drop the pronoun ты and just use the "you" form of the verb (думаешь) to express a general truth or observation. It works exactly like the general "you" or "one" in English (for example, "longer than one expects").

Why is the comparative adjective длиннее used after оказывается instead of the Instrumental case?

The verb оказываться (to turn out to be) usually requires the noun or adjective that follows it to take the Instrumental case. However, simple comparative adjectives ending in -ее (like длиннее) are invariable—they are "frozen" and never change their endings to match case, gender, or number.

Could оказывается be used as an impersonal introductory word here, like "It turns out that..."?

Not in this exact sentence structure. Here, оказывается is the main verb attached to the subject дорога ("the road turns out to be..."). If you wanted to use it impersonally, you would need to rephrase the sentence with a subordinate clause: Оказывается, что дорога всегда длиннее... (It turns out that the road is always longer...).

Why do we use чем (than) here instead of just using the Genitive case for the comparison?