Эта статья довольно длинная, но я прочитал её почти до конца.

This article is quite long, but I read it almost to the end.

Breakdown of Эта статья довольно длинная, но я прочитал её почти до конца.

• я: I
• длинный: long
• но: but
• прочитать: to read

Questions & Answers about Эта статья довольно длинная, но я прочитал её почти до конца.

Why does the adjective длинная end in -ая here?

Because длинная is modifying статья, which is a feminine noun in the nominative case. In Russian, adjectives agree in gender, number, and case with the nouns they describe. Since статья is feminine singular nominative, the adjective also takes the feminine singular nominative ending -ая.

What’s the nuance of using довольно instead of очень?

Довольно translates roughly as “quite,” “fairly,” or “pretty” in English. It indicates a moderate degree, less strong than очень (“very”). So довольно длинная means “quite long” (implying it’s long enough to be noticeable), whereas очень длинная would be more emphatic: “very long.”

Why is the verb прочитал used instead of читал?

Russian has two aspects for past actions: imperfective (читал) and perfective (прочитал).

• Читал (imperfective) would mean “I was reading it” or “I read it (habitually).”
• Прочитал (perfective) means “I finished reading it.”
  Here the speaker suggests they got almost to the end, so they use the perfective прочитал to show a completed action (even if not 100% complete).