Is there some sort of trusted trader or a place where i can keep them ? Everywhere i read its full of warnings not to trust anyone and always guard your coins and stuff.
This kind of question is what the warnings are all about. Of course there are trusted users on the forum but it is best to not having to trust others. Because if they take your coins you have not much you can do against.
If you want to sell your best bet would be to use one of the big exchanges. Like kraken.com, bitstamp or bitfinex. Don't let your coins lay around there, hold them safe in your computer without viruses and such. Then when you want to sell send them to the exchange, exchange them and withdraw the fiat money.
Or if you need cash you might use localbitcoins or the mycelium app that includes a similar service like localbitcoins. You then can meet a trader at a McDonals or something, search a calm edge and exchange the money so that not everyone can see it.