If you doubt it, they are probably not genuine. Unfortunately fleaBay has several forgeries for every genuine item. Such an easy way to sell them and many people are taken in thinking that they have a bargain. People get mesmerised by low prices and 'cheap' and pitch common sense to the wind.
I'm afraid that you have bought a second hand suit which does not fit you. Cut as well as style/size are all equally important.
Put it back on fleaBay or if you did not pay much above its real value $5, £3 just burn it and spare yourself the effort.
Chinos, woollen trousers given that there are all manner of degrees of 'casual' and that term does not carry any meaning whatever. In fact it is probably correct to say any pair of trousers other than suit trousers can have a place within 'casual'.