the expert only buy , its doesn't enter any sell !!

what I would suggest is that you add more intelligence to the expert for example
now the expert open a trade whenever it close a trade which is fine and is good for a trend following idea, but why not accept a loss of lets say 200 pips and when a loss happens , this means there is a trend change so you switch from only buy to only sell.
meaning you remember the last trade and if that trade is a winning trade you keep trading on the same direction , if it was a losing trade you swicth

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