Thank you both. optimize has to be placed after "asset" call.
Code
	assetList("AssetsDarwinexFMB");
	asset("CHF/JPY"); // GBP/USD
	Stop=optimize(3,1,10,1)*ATR(20);  // 6.01
	TakeProfit=optimize(3,1,10,1)*ATR(20); // 2.88

This way works fine.