What is the purpose of Newspeak?
Language is the way we think and communicate; the wider the range of words, the more likely we are to find a way to express various thoughts. The purpose of Newspeak is simple --- limit/control the words that are available for the people's use, and you will limit their thoughts and their ability to communicate with each other. Eliminate the words that you do not "like," words such as freedom and liberty, and introduce words that do not exist and give them a "temperature" that makes the thoughts desireable or undesireable. A good example is "oldlife" which refers to a person's life in the "old" times --- and oldlife is not something that is positive ... it suggests the time when Big Brother was not taking care of us, protecting us from Goldstein, a time to be forgotten.
The ultimate goal is to remove all language/thoughts that could be harmful to Big Brother.
NOTE: although we don't have Newspeak, we do have politically correct speech and our politicans are always changing the meaning of words to fit their needs. Maybe we do have Newspeak ....