Generally, it takes 80 to 180 days for IRCC to process a PGWP application. However, while waiting for the decision on your application, you are eligible to work in Canada, given that you have already applied for this permit before the expiry of your study permit.
In total one has 180 days to file an application for PGWP from the time you completed all the requirements of your program of study.
Unlike earlier rules, if you have left Canada on the completion of your studies, you are still eligible to apply for a PGWP from overseas. If one submits a PGWP application from overseas, IRCC will require them to provide additional supporting documents based on the visa office that will be processing the application.