Uh-oh 
Slang is fine, but we’ll have to keep it SFW. @cleah89, you are well informed, haha - who are you hanging out with?!
Indeed, in Portugal, we only use “fixe” for “cool”, never “legal”. “Legal” to us is only used in, well, legal contexts. “Fixe” can also be more or less used to say “OK”/“All right”.
Just one correction and a note regarding your comment, @cleah89: 1) It’s “ela tem muita lata” (not because it’s a female subject, but because “lata” is a feminine noun); 2) “Vá-se lixar” is formal. You can use it when speaking to someone you would treat as “você”. Otherwise, just use the informal “Vai-te lixar” (to one person only). For two or more people, whether informal or formal, “Vão-se lixar”.
Let me think of more stuff we can say… Any specific sentences you’d like to have translated, @nicolebgarcia?