How can I lose all my money on a reputable and well renown platform? Are they not responsible for the coins that they keep for their customers ?

Mt. Gox, Cryptsy, and many others. Any money that you keep on an exchange is not your money, it is an IOU. Do your research.

How can I best keep my coins even Golem (not supported by hardware wallet I think) ?

Wrong thread.

Also I think every time I withdraw my alt-coins from those platforms, they charge some fees or not?

Again, wrong thread. Don't post off-topic stuff in here anymore.