Design an App Mockup

We're looking for a simple webapp mockup - we're mainly focused on desktop for now, but responsive designs will be prioritized. This webapp handles problems in organizations. Any user can see all problems, any user can post problems, notifications are sent to users with matching skills and the job can be accepted. Problems have a creator, date of insertion, difficulty rating (1-5), title, description, required skills, users trying to solve, comments, and suggested solutions (either similar past problems or information retrieved by the system from the web). We need 3 essential views: the problems list view, the single problem view (possibly via an in-page popup - modal), and the problem insertion form. If possible we would like to have a user profile view page design with statistics: username, e-mail, full name, number of problems solved and acquired skills. We feel we need a full width header and footer bar. The header would display on the left the webapp's name logo and on the right, icons for problem notifications, general notifications and settings (which would include logout, profile and settings). The header would allow for access to a hideable sidebar through a small icon on the left of the logo. Please provide any questions you have for further information.