If I download a movie on Netflix and then it gets removed do I keep it forever

No, if you download a movie or show from Netflix while it's available, you can only access that content for a limited time. Even if you have it downloaded, if Netflix removes it from their library, you will not be able to watch it once your download period expires or if you delete the download. Downloads are subject to the availability of the content on Netflix, and they typically have an expiration date, regardless of whether the title remains available on the platform.