Will My Shop/Home Wiring Be Overloaded One Day?

Everyone and his brother here in Mexico call themselves electrician/plumbers. I don't trust hardly any of them. First of all, why such skimpy wires to begin with? I don't know, will have to ask them.

But then you can't find the guy that did the work in the first place. Blame the wife, she finds these cut-rate workers because she's cheap and I have to came back and have things done over time and time again. The wires run through concrete and cinder block so it's hard to see what's going on under there.