> . . . I've read that the spinning spaceship (Circular disc) will not be useful, because; issues

There's nothing that makes spin-gravity a show stopper unless the habitat in question is very tiny and rotating fairly quickly, but it's also not a strict requirement for a mission to Mars and that's why it's seldom considered in detailed plans for manned missions to Mars in the near future.

Assuming the slowest normal trajectory (assuming you're not using a very low thrust but still man-rated electric rocket), going to Mars or returning from it takes about eight and a half months. There have already been human beings that have spent more time than that in space within individual missions, and they also fully recovered from any negative effects.

There, however, remains a question mark in regards to how deleterious Mars gravity may or may not be towards the human body. It's quite possible that some gravity, however low, may be enough to stave off the effects typically seen with extended periods of living in zero gravity. Very little observational data on the subject exists, however.