I think I should hire employees later.

I hired employees while watching ads and upgraded them a lot, but I found out that experience points only increase when I sell myself, not through employees? Whenever I tried to sell, the employees kept taking them. Since I had already mined everything possible and couldn't mine anything new, I filled up 50 items at a time through ads and barely gained experience points while rushing to pack my inventory before the employees... Hire the coal mining employee first and then hire other employees slowly.