A few weeks ago, I was given a bonsai as a gift, (my first - so I am not very familiar with how to care for it) and am keeping it in a very sunny location. It has recently begun to sprout new longish branches, changing the overall shape. Is it OK just to prune them back so that it retains the original shape?
It is difficult to give proper advice without more specifics. Firstly, what species is it? Of less importance regarding your specific question but still relevant, what is the soil like? What is the climate like where you live?