I do not see the Critical Path and some other functionality, how can I enable that?

Licensing & Purchasing
Apparently you have a license for the Pro edition.
The Critical Path functionality is available in the Enterprise edition.

The full list of features available in the Enterprise edition only:
  • Critical path
  • Enhanced security that includes password policy, user lock due to inactivity, etc.
  • 100 GB of storage space (for hosted plan only)
  • Resource Loading Simulation
  • Time Logs approvals & lockdown
  • Unlimited portfolios
  • Unlimited custom fields