ssd upgrade dell inspiron 7559

Sorry, for some reason the link didn't work.  Trying again: https://www.dell.com/community/Storage-Drives-Media/Inspiron-7559-not-detecting-Samsung-960-Evo-M-2/m-p/5135858

That thread also includes a recommendation to an appropriate SSD for your system, namely the Samsung 850.  That's what I would recommend as well, but make sure you get the M.2 version, because the Samsung 850 is also available in mSATA and 2.5" (laptop size hard drive) form factors, neither of which would work for you.  You need the Samsung 850 M.2.

Those aren't opposite things.  M.2 is the type of connector.  SATA is the actual protocol that the SSD uses to communicate with the system -- M.2 SSDs can use SATA or the much faster NVMe/PCIe, but not all systems with M.2 slots support the latter.  And "2280" refers to the physical size of the card.  The vast majority of M.2 SSDs on the market are 2280 because the vast majority of systems use that size.  According to this thread, the Inspiron 7559 does not support NVMe, so as long as you bought an M.2 SSD that was size 2280 and used SATA rather than NVMe/PCIe, you will be fine.