You can find out how our ranking system works here. That link will show you exactly how we calculate the ranks, as well as how our seasons, leagues, and matchmaking work.
In your case specifically, the rank you have is generally too high for the competition you have been facing. Our Arenas seperate themselves not only by currency but also by skill/rank level. Arena 1, predominantly, is the weakest arena especially for the rank you have. Arena 2, then 3, rise in skill/rank level, in that order.
I recommend venturing into higher Arenas(2/3). You will be playing harder players with higher ranks which will reduce the risk factor for you. Winning will award you more points and losing will take away less points.