Is it enough so that I have peace of mind about memory problems and after what period do I have to upgrade?
240 GB of storage is really not much. Fortnite is definitely not enough. Certainly not for "rest" from memory problems. In addition, you can't have many programs
I would recommend a 1 TB hard disk, which you then partition (1 partition only for Windows, 1 for programs and 1 for your own files)
What is a partition?