A homework assignment

Hello. I was given an exercise at school and wanted an opinion or 2 before I turned it in. We were given sentences to correct and this is what I came up with. Does anyone see any mistakes or something I might of missed. I appreciate it.

1. Our company's management council had all ready decided to appoint an investigative team; however, they acted too slowly.
2. Organizations are forming teams for at least 3 good reasons; better decisions, faster response times and increase productivity.
3. Most teams go through 4 development phases: forming, storming, norming, and performing.
4. Some group members play dysfunctional rolls and they disrupted the groups progress toward it's' goal.
5. Successful self directed teams are autonomous, that if they can hire, fire, and discipline their own member.
6. Although we tried to reach consensus, several Managers and even the Vice President opposed the whole proposal.
7. At last months, Staff meeting the CEO and him complemented the team's efforts, and made warm supportive comments.
8. Rather than schedule many face to face meetings, the team decided to invest in three thousand dollars desktop video conference system.
9. When conflict erupted at our teams January meeting, we made a conscious effort to confront the under-lying issues.
10. 55 people are expected to attend the Training Session on April 15th; consequently, she and I must find a bigger room.