How quickly can I change my body and grow muscle?

There are lots of factors that will impact how much and how differently each individual will grow. There are some estimates about what you can expect on average but these are only intended as rough guides. A basic estimate for new lifters is about 2lbs of muscle growth a month for males and 1lb a month for females; for the first year of training. These numbers will vary with height, starting weight, training, diet, genetic and more. If you want to get a rough idea of how much change you could expect at different stages in your training then there is a more detailed explanation here:

Keep in mind that these models are merely guides and will always be mediated by genetics, training, skill and recovery protocol.