Still stuck in the "Rainy Factory" at level 55.

It's truly amazing how you've upgraded the electronic cannon to the 4th tier without spending any money. It shows incredible dedication. This part is tough, but with that perseverance, you'll overcome it brilliantly soon. I'll always be cheering you on.

If your combat power is too low, you might not be able to clear it. Alternatively, you could try investing your stats differently from the start. Securing firing speed and reload speed early on is surprisingly important.. Have you activated all the other features? Like the robots or ongoing events.. The shops are scattered in various places, making them a bit hard to find, but if you've been playing consistently, you should have accumulated a lot of tokens here and there.

Why is it only +4? Did you perhaps leave the previous weapons' enhancements as they were and enhance the new one without transferring the enhancements?