1.
Q.What would happen if everyone wanted to be the leaderin a group?
A.We will get big problem.

CORRECT:

Q.What would happen if everyone wanted to be the leader in a group?
A.We would get big problems.

>>There should be a space between words. Be consistent with your verb tenses. When talking about things in general, plural form of nouns should be used.

2.
Q.Are team member less important than the team leader?
A.No.team leader and team members are all important.

CORRECT:

Q.Are team members less important than the team leader?
A.No, team leader and team members are all important.

>>Plural subject takes plural verb. Be mindful of the correct punctuation mark. A period is used to end a statement.