how to update ssd in xp15

Yes that upgrade would make a significant difference.  The 128GB SSD is M.2 SATA, whereas the 970 Evo is M.2 NVMe.  Even the best SATA SSDs can only do about 550 MB/s (and that 128GB SSD might not be a top-end SATA SSD), whereas NVMe SSDs can do more than 3 GB/s.  And the performance difference would be even more significant between the 1TB HDD and an SSD, since HDDs can typically only do about 120 MB/s.

If you want to run Linux, you'll need to switch the SATA Operation setting in the BIOS from RAID to AHCI.  The factory default is RAID, but Linux doesn't have the Intel Rapid Storage driver that's required for RAID mode  -- and despite the "SATA Operation" name, that setting also affects NVMe SSDs.  Note that if you change this setting, it will render your existing Windows installation unbootable because that setting is intended to be changed before you install your OS.  If you plan to reinstall both Linux and Windows, then this won't be an issue.  If you would like to keep your existing Windows installation, there are some steps you can through through that would allow you to switch from RAID to AHCI and "fix" Windows afterward.  I think you have to go into Safe Mode before or after the change to make some changes, but I haven't looked at this in detail because I always just set that the way I want it before I install the OS.

can i keep windows in m.2 ssd and and install linux in the new 2.5"  ssd , how would i have to config bios for that  ? will i need to make any changes in bios  if i swap the default m.2 sata ssd with the samsung one ? 

@kstsid  although I've done multi-boot setups in the past, I've never done it in a way that had different OSes on completely different disks. But there are some things you'd want to be aware of if you want to go that route.

First, even if you want to do that, the typical setup is that you'd still have a single bootloader on one of your disks that would then allow you to choose which OS to load.  For a Windows/Linux setup, typically you'd use GRUB.  So from a BIOS/system perspective, it would always boot to the disk that contained GRUB, even if you then chose to load the OS that was installed on the other disk.  The reason this is typically done is so that you have an easy way to select between your OSes at each boot without having to mess with BIOS settings or manually invoke the system-level one-time boot menu (by pressing F12 during startup).  The catch to this setup is that if you ever remove the disk that contains your single bootloader (or something happens to it), then you don't have a way to directly boot to the OS on the other disk anymore, because that disk likely wouldn't have its own bootloader.

The alternative would be to set up the two disks completely independent of each other, where each disk has only the bootloader for the OS that resides on that same disk.  So you end up with two bootloaders, each of which only boots a single OS.  This gives you more independence, but less convenience, because now have to have the system boot to the desired bootloader whenever you want a specific OS.  So you'd essentially have to choose a "default" bootloader for your system to boot to and then use the F12 one-time boot menu whenever you wanted to boot to the other OS.  In addition, multi-boot setups typically do NOT set themselves up this way specifically because this setup is less convenient and also much less intuitive to average users compared to having a single bootloader that knows about both OSes.  So if you wanted to set your system up this way, you might have to make sure only one disk is physically installed during each OS installation so that they're not aware of each other when they're setting themselves up.

In terms of what you have to do in the BIOS, if you go with the first and more common option, you shouldn't have to do anything in the BIOS except maybe disable Secure Boot, since most Linux distros don't support it (although some do).  If you want to use the second setup, then it gets more complicated because newer systems like yours use UEFI booting, which works very differently from Legacy BIOS booting.  In BIOS booting, you choose a device you want to boot from.  In UEFI booting, you choose a specific bootloader FILE on a specific partition of a specific disk, and those bootloader files have to be registered into the firmware.  Typically this bootloader file registration is handled by the OS installer, so if you install each OS separately (with only one disk installed each time), then both bootloader paths should get registered into the firmware automatically, and then you'd be able to reorder them as you want.  But if not, you might have to manually add a boot option by selecting the appropriate bootloader file for whatever bootloader you decide to use for each disk.

thanks for such a detailed answer, i plan to replace the default ssd with a samsung nvme pro , do i need to make any change in bios for that ??