It works like this
1. person A creates a project
2. 10 freelancers applies to it with their proposals 
3. person A chooses one freelancer from them (person B) 
4. he then prepays negotiated sum to cgtrader (full amount) 
5. person B gets notified about that by e-mail and can start working on the project 
6. when job is done, person B uploads all the files through project dashboard 
7. if person A is satisfied with the job, he marks the project as finished and payment is released to person B

