Relativity is a difficult subject. Even simple cases are difficult to tackle. I would suggest that before looking at complex situations, you start looking at simple cases to begin with. Here are two simple cases:

1) Twin paradox. See: http://soi.blogspot.com/2011/09/twin-paradox.html
2) Faster than light violates causality. See http://soi.blogspot.com/2011/09/why-...causality.html