I have a friend who started trading throw a trading company and made some profit , is it a profitable activaty or a risqy ?

if i understood it correctly you can buy at www.bitstamp.net and sell at www.portbitcoin.com with profit.

Current situation for buying 1 btc:
price at www.bitstamp.net : $318.93
fee: 0.44% = $1.7
total: $317.23

Current situation for selling1 btc:
price at www.portbitcoin.com : $328.95
fee: $1
bonus code BITRIP293 boost: 5% = $16.4
total: $342.35

Total profit = $25.12

I believe i did the right math. This seems to be a good way to start trading with profit.

sounds good. did you try it?