To see how much storage (not memory - that's RAM) you actually have to use, see
[Guide] Checking the ACTUAL storage space on an Android device. You don't get 256GB for your use, storage is partitioned for a number of things, and you get one partition to use. Android and a lot of other things get the other partitions. (You should have more than 16GB, though. There isn't even a reasonable maximum file size limit - it's 16TB [16,000GB]. By the time we have files that large, we'll most likely have a different file system with a larger filesize limit.)