Hi @mahzaz
Here's the [document|34909|hardware maintenance manual] for the laptop.
Go to p.67 in the manual (74 of 109 pdf) to view the procedure to remove the sata HDD which can be replaced by an up to maximum 4TB 2.5" sata SSD.
On p.70 in the manual (76 of 109 pdf), it describes the procedure to remove the M.2 SSD if there's one installed. If there isn't one installed then you can insert an up to maximum 4TB NVMe M.2 2280 SSD, so that there are 2 SSDs for storage use in the laptop.