How do I deal with increasing number of staff?

I run a small road construction company that currently handles simple asphalt laying, along with everything related to that process. My main customer is the local municipality. Larger road construction companies typically take on bigger projects, such as building new roads from scratch, which involves underground work like laying cables, pipes, and installing pillars. To grow my company, I’ll eventually need to take on these kinds of projects, but that would require hiring engineers and additional specialized staff.

As of now, the company is divided into three departments: operators and mechanics working at the asphalt plant, workers and drivers on the road, and office work, which is entirely handled by me, including documents, invoices, project coordination, and many more.

As the owner, I have to manage all three departments while also maintaining supplies, meeting new clients, and keeping track of everything. So far, I’ve managed to handle it, but there’s a major issue: about 95% of my staff (currently around 15 employees) are unproductive unless I’m directly supervising them. If I’m at the asphalt plant, the road workers tend to slack off and do very little, even if I’ve given them specific tasks. They often make excuses like a machine broke down and needed fixing instead of completing the work. The same happens when I’m on the road — the plant workers don’t get much done either.

Next year, with more projects coming in, I’ll need to hire around 10 additional employees to keep up and grow the company. But the bigger issue is that I’m in Bulgaria, where unfortunately, most workers tend to be lazy and untrustworthy. Hiring supervisors or managers is difficult because they’re likely to steal or lie. Increasing salaries isn’t an option since everyone is already paid above the market average.

I’m really anxious about how I’ll handle more projects without wearing myself out by trying to be in three places at once, while still maintaining quality and standards. How do you manage multiple departments and improve productivity when it feels like it’s close to zero? Is there any technology or system I could implement to help? I would really appreciate any advice.