urineun seoro doumyeonseo iksukhaji anheun ireul yeonseuphae.

• 서로 means “each other/one another.” It marks reciprocity between members of the subject (here, “we”), i.e., they help one another.
• 같이/함께 mean “together,” focusing on doing something jointly, not necessarily for each other. Examples:
• 우리는 서로 도와요 = We help each other. (reciprocal)
• 우리는 같이 일해요 = We work together. (joint action, not necessarily reciprocal help)

-(으)면서 most often means “while/as,” indicating two actions happening at the same time by the same subject. Here: “We practice unfamiliar tasks while helping each other.” Note: -(으)면서 can also show mild contradiction in other contexts (e.g., 알면서 왜 그래? “You know it, so why act like that?”), but here it’s pure simultaneity/manner.

• 우리는 sets “we” as the topic (“as for us”), giving background and sounding neutral/natural.
• 우리가 highlights “we” specifically as the doer, often used for emphasis or contrast (e.g., “We (not others) practice…”). Both are grammatical; the nuance differs.

• 연습해: casual/informal (banmal).
• Polite: 연습해요.
• Formal: 연습합니다.
• Plain/written declarative: 연습한다. So the whole sentence can be:
• 우리는 서로 도우면서 익숙하지 않은 일을 연습해요. (polite)
• 우리는 서로 도우면서 익숙하지 않은 일을 연습합니다. (formal)

• Base descriptive verb: 익숙하다 (“to be familiar/used to”).
• Negation: 익숙하지 않다 (“to not be used to”).
• Attributive form modifying a noun: 익숙하지 않은
  • 일 → “work/tasks that (we are) not used to.” Alternatives:
• 낯선 일 (“unfamiliar/strange tasks”)
• 익숙하지 않은 것(들) (“things we’re not used to”)

As a predicate, it takes 에: 이 일에 익숙하지 않다 (“not used to this work”).
When used attributively to modify a noun, you typically don’t include 에: 익숙하지 않은 일 (“work [we’re] not used to”).
You can also make a fuller relative clause: 우리가 아직 익숙하지 않은 일 (“work that we’re not yet used to”).

• 돕다: “to help” (basic verb).
• 도와주다: “to help (someone) as a favor/for someone’s benefit,” adds a “give/do for” nuance. With 서로, both are fine:
• 서로 돕다 and 서로 도와주다 are both natural. 서로 도와주다 can feel a bit warmer/more colloquial.

• -며 (도우며): More formal/literary; often used in writing or news.
• -고 (돕고): Lists/links actions; can imply sequence or simple addition rather than clear simultaneity. To emphasize “while/as,” -면서 is the most natural in everyday speech.

일 is broad: “work,” “task(s),” “matter(s),” “stuff.”
In 익숙하지 않은 일을 연습해, it’s best read as “unfamiliar tasks/things.” If you want to stress “various tasks,” you can say 일들, but Korean often leaves plurals unmarked.