Don't worry about going too fast or too slow. Make it as long as you feel you need to be. For if the story needs information but you cut it to make it fast, you will probably omit information. If some part of it is meant to be short, don't make it longer, because you won't know what to do to fill it in.
Make it as short or long as you consider necessary. My novel is 139 chapters long, I feel I'm just finishing the beginning and my readers say I'm going too fast, too much too soon. In short, just do what you think is necessary, nothing more, nothing less.