語る and 話す: telling experiences
Compare 語る for telling experiences or thoughts with the broader verb 話す.
Telling experiences and thoughts
語る (かたる) is often used for recounting experiences or expressing thoughts in some depth. 「祖父が若いころの思い出を語りました」 says that the grandfather recounted memories of his youth.
「将来の夢を語り合いました」 means sharing dreams for the future with one another. The 語る family can describe reciprocal conversation too.
Ordinary conversation
話す (はなす) broadly covers conversation and speaking a language. 「友達と少し話しました」 says that the speaker talked briefly with a friend. Replacing it with 語りました can emphasize telling something with substance.
「電話で話しました」 means talking on the phone. The content is separate; the medium alone does not determine depth or duration.
Not just a matter of length
Both 「夢を語る」 and 「夢について話す」 can describe talking about a dream. 語る is not necessarily a long monologue, nor is 話す empty small talk. The focus differs in what is told and how it is presented.
「経験を語ってもらいました」 means having someone recount their experience. Distinguish the experiencer from the listener rather than treating it as the speaker's own experience.
Which verb is usual for saying 'I can speak English'?
Show the answer and why
「英語を話せます」 is natural. The two verbs are not interchangeable in every sentence.