What make/brand is this bike marked "Challenger" and "Resistance"?
The usual method of identifying a bike is what you've done. 

The brand and model are usually part of the decals on the frame. 

My bike, for example, says Scott on the downtube, and CR1 Pro on the toptube near the headset. 

It is Swiss made, and the model stands for comfort road 1, and Pro tells you what parts were on it originally. 

If there are no decals, an experienced mechanic or shop owner can usually identify most common frames. 

Your bike is very basic, at best, and most people would not consider it safe for use on off road trails. I would recommend looking for a shop quality mountain bike. You will enjoy riding more, and that is what it's all about.  Feel free to ask if you need more information.