Firstly take on all the points Faris Udeen is telling he’s spot on.
It’s not true that martial arts or a certain martial art can give you a rough manly look. It all depends on what you want, if you want to be as hard as nails and want to be 100% sure that if you were to fight you’d win then you have to put yourself through certain things. I had to show I could break my fall outside on concrete in order to grade.
If you want to do something for fitness and want something that’s gentle I’d look at Tai Chi.
If you’re interested in that sports aspect then Taekwondo and Judo are probably the best.
The benefits are fitness, discipline and the ability to protect yourself. As far as how long it takes to learn it depends what your goals are I’ve seen a white belt defeat people with higher grades, for some people it’s when they get up to a certain level of fitness.