Electricity Problems

Hah , one of my couplers just burn out . There was a big cloud of smoke , good I was here when that happened ... My ask is what I have to do that this problem will not more happen ?!? To use new couplers with bigger wires ? How big/widht have to be the wires and pls tell some advice to not burn my house . My fuses stop imidieatelly but , I dont wanna to reach this level of protection . Thanks
p.s dunno how the font start to be red ...

Couplers? Whats that?

I dont know the exact word for this item , thats why I only translate it in google-translate. Only found this word for now ... Its a multiple contatcs with wires[FONT=arial, sans-serif][/FONT]

Burning plug is probably from a lousy contact causing arcing. Install new plugs male and female.

yeah , this one was really old , but it was working till now , its kind of 15-20 y old
I knew it someday that will happen but I thought if some item work properly so many time , this means is good enough , but I was wrong ...