Help on calculating percentage based on multiple criterias

Dear Sirs,

Request help on excel formulas i have to prepare a excel sheet as attached based on following criteria. I hope i am not asking for too much, but i have no better platform. Thanks in advance to all..!!

In Main Sheet user has to fill all the values/info. Project belongs to a Concessionaire, A concessionaire can have multiple Projects

User has to complete all the Tasks assigned to a project and accordingly percentage of progress/completion will be reflected for project as well as corresponding Concessionaire also

Percentage for a task has been defined , as the tasks are getting completed progress will be shown in Summary sheet , if the last and ultimate task is completed without doing initial tasks, all the tasks shall be considered as 100% Complete, and progress will be 100% for project and subsequent percentage shall be add to concessionaire based upon no. of projects concessionaire have.