Let me point out what is wrong with this A) theories are tested hypotheses, they can be proven just as evolution was with generations of creatures that reproduce quickly making more generations faster B) a fish would not develop legs to move onto land, it would develop legs from living on land, they only develop to benefit themselves in their current environment. C) they don't evolve mid lifespan, it is slight changes in DNA that changes traits, those with bad traits die off and good traits are passed on through reproduction. D)you don't fully understand evolution, which is my problem with most creationists. However you did at least get a simple understanding so I can respect that, just look further in depth and you should understand it better