If you see that in your house it's time to invite an electrician.

Went to basement while been going to change fuse box for client and found broken cable has been connected by screw terminal block and covered by insulation tape. Terminal has raiting 15 amperes and been waiting to melt because this is sockets circuit protected by 32 amperes circuit breaker.

 
So I've used Wago connection box and made installation much more safe.
At the and client get new consumer unit and certificate.