what if you don't know anything about a default jugdement against you, and the citation is forgied signature

Answer 1

Go back to WHATEVER court placed the judgement and ask how to have it set aside

Answer 2

The procedure for seeking to set aside a default judgment is entirely dependant on the laws of your unknown country.

(And on the State or Province if it's a Federal country such as the US, Canada, Brazil etc)

Richard