Plumbing and heating engineering company seeks complete solution

I have two legally independent companies in the field of plumbing and heating, customer service, and maintenance, and I am looking for a complete software solution to support my daily work. Both companies should run on the same program, as they are both in the same industry. In general, paperless and faster working practices should be introduced in both companies (keyword: “digitalization in the skilled trades”).

I have the following requirements for the software:

• Quotes
• Invoices
• Dunning
• Controlling
• Create all work reports on site at the customer's premises using a tablet, smartphone, or similar device, sign them, and send them to the customer immediately by email (copy of work report)
• Assign measurements, photos, and sketches to the customer for better documentation and archiving
• Sending quotations, partial and partial invoices, as well as work and cost reports, mostly by email in future
• Compliance with the latest legal regulations for data protection and archiving
• Existing billing and calculation software is to be replaced
• Multi-client capable, as two (possibly a third) legally independent companies are to work with the software
• Windows-compatible
• Mobile access
• Fibu interface (Agenda) is an advantage

Two office workstations and two mobile software workstations are planned.