“change.” The Hebrew is “turn.” It may mean “restore” (HCSB), but that may be too much. It does mean “change” (ESV).
“speech.” The Hebrew is “lips,” here put for what is spoken by the lip, “speech” or “language.” The pure language does not mean Hebrew will be the universal language. The language people will speak in the future is unknown. The pure language in this context is the language of praise and honor to Yahweh, the Creator of all.
“shoulder to shoulder.” The Hebrew is idiomatic, “with one shoulder,” and thus picturing the people crowded together serving Yahweh and calling upon Him in worship, bowing down before Him together. However, the idiomatic phrase “with one shoulder” is somewhat unclear in English, and we often render the concept with the phrase “shoulder to shoulder.”