Bianchigirll 

Hello shark43, welcome to the forums. this may be a better topic for the general cycling forum but I will ansers your questions. also welcome to the great outdoors.

first off I am not sure where you live but in most states and towns bikes are generally consider vehicles and therefore subject to the same rules of the road as cars. I do hope you are riding with traffic, obeying stop lights and signs and signaling your turns. being on the sidewalk is often not the best place to be but we all do it for short distances sometimes.

as for your bike although the pics are a bit blurry I do not think there is anything wrong with it. chances are the original owner just did not like cycling or did not have time to use it.

this bike is what I would call an 'all arounder'. it was designed with the idea that the owner would mostly ride on the street or local cycling paths with an occasional dirt road or trail thrown in. it not reall a mountain bike but could be ridden on a dirt trail. there is no reason why with a bit of practice and confidance you can not handle the occasional patch of sand on this bike.

I would recomend going back to the shop and have this bike tuned up and adjusted to fit you, unless it is too big for you. the seat looks really low (which could mean it is too big) and the handlebars can be repositioned to make them more comfortable to hold.

spending $40-50 to tune up this bike and make it better/more comfortable to ride until you decide if you like cycling in the open air is, IMHO a much better investment than $350+ on new bike that may end up collecting dust.