Not really connected to the thread but...blue font on blue background it's a very, very bad idea for contrast and accessibility (e.g. "Strength").
Please revise that :P
You can't use || in that way, you need to give some random also in that specific case. It should be something on these lines:
public Item GiveFish( double skill )
{
if ( 0.038 * skill > Utility.RandomDouble() ) return new RockLobster();
if ( 0.040 * skill >...
You must have done something wrong while importing them, cause all those ";" are not missing.
Also I don't think it's useful to post errors in Italian, not everyone would be able to understand.
I believe you forgot to give an exit in case the tokens are not 50. Try changing the backpack code to the following:
Item[] items = p.Backpack.FindItemsByType( typeof( Daat99Tokens ) );
if( items.Count() >= 50 ){
for (int i = 0; i < 50; i++)
item[i].Consume();
} else {...