Cannot understand how backtesting works

Hello guys

I've just started using calgo for my but. I had a c# version I did by my own and this is a porting. 
I have some problems with the backtesting as I always and up with negative equity as you can see in this chart:

I can see in the history that 95% of the trades are winning trades. Does this mean that there are many open trades that are still not closed and are loosing very bad? I did set up a basic stop loss system so they sould close if things go really bad.