It isn't clear what "hitting so much" means. First, the system will run better with the 8G module removed, leaving only the 32G.  That way, 32 G RAM will run at full bandwidth.  With 8+32, only 16 G RAM of your total is running at full bandwidth.  The rest is running at  half bandwidth. Second, if the issue is slow performance in games or under heavy load, has the system been thoroughly cleaned internally, with replacement of the thermal pads?  It's around 3 years old, meaning it's overdue if it hasn't had internal maintenance. If you need more storage, by all means upgrade the SSD -- and yes, 2T will work.  The new SSD will not run any faster than the original as the system is old enough that its interface is PCIe 3X4 -- not the PCIe 4X4 that newer drives are capable of.  
HI all, i am using Dell G5 15 5590. Can i upgrade my ssd 256 gb m2 to Samsung 970 SSD 2 tb in my laptop is it comfortable for my laptop without any issue or not. if i upgrade so how my much we update pls give me good suggestion i also update my ram 16 gb to 40 gb updated but its hitting so much i don't why . any solution? 
SSD upgrade