what do you think of the result of this expert
is it giving good signal
should i trade with a bigger size to maximize profit
as you see the expert made only 9 trade since january 2018
9 trades is nowhere near enough to draw any conclusions. Tell this expert to show you his stats after 500 or more trades.
If you are just beginning, stay away from EA and learn to trade first 
and when you have a successful system then create your own EA.