I'm not sure, but my impression (please correct me if I'm wrong, okay? ) is that RiX was asking whether having a threesome could change someone's sexual orientation from gay to straight or vice versa.
It's generally thought that sexual orientation is fixed pretty early on in life, possibly before birth, and is not something people can just choose to change. So it's very unlikely that any experience (sexual or otherwise) is going to magically "change" someone's orientation.
However, some people do discover that their perceptions of their orientation change during their lifetime - for example, they might initially think they were attracted only to one sex, then find out that they can also be attracted to people of the other sex too.
do u think u would change being ether gay or being normal?
Being gay (or lesbian, or bi) is just as "normal" as being straight is.
like 3some is nasty or do u think u would have fun?
Personally, I wouldn't label any safe, consensual sexual activity as "nasty". But different things work for different people. Some people choose to have multiple partners; others are only comfortable being sexual with a single partner.
And even if you like the idea of a threesome, the reality can potentially involve a lot of emotional and sexual complications. Check out these threads for explanations of why: