convert flat roof to a pitched roof and installing solar on pitched roof on a 13 story high residential high-rise building

I am looking to convert my flat roof to a pitched roof and to install solar panels or solar tiles on the now-pitched roof of my 13-story high residential high-rise building. The current material of the flat roof is something other than concrete or asphalt. The desired pitch of the new roof requires further consultation and design consideration. I need the project completed as soon as possible. Therefore, I am looking for reliable freelancers who can take up this project and convert my roof with utmost proficiency and complete it within the required timeline.