Construction company seeks project management software (Gantt)

We are a construction company specializing in residential renovation (serial projects) and are looking for Gantt-based project management software for our projects. We offer services including all types of floor laying, electrical installations, drywall construction and interior finishing, plumbing, and painting and varnishing.

The software should meet the following requirements:

• Full Gantt functionality (dependencies)
• Gantt multiproject resources Workload scheduling
• Possibly buffers, task split
• Multiproject views
• Always 50 projects (rolling) with 15 tasks
• 50 resources (by role/function), possibly virtual resources (flexible outsourcing)
• Daily resource planning
• Workload
• Project development
• With API interface to transfer data to ERP, etc.
• Visually display resource overbookings and resolve them on the same screen, or split screen, or two screens with immediate updates
• In case of overbookings, suggest other available resources with the same role/function or schedule virtual resources (flexible outsourcing/flexible additional booking)

Extremely important:

- A task is created as 1 day with resource 1

- If the task is now extended to three days, the effort must increase from 1 to 3 days and not be divided. (Many programs do this, but some do not)

• Browser-based

Three software workstations are planned. MS Windows systems are used.