I heard from client that Firefox takes big chunk of 4gb memory which seems to be corroborated by your screenshot. For Firefox get at minimum 8 gb ram. for ddr4, community recommendation is crucial ram guaranteed to work or $back.  No need to buy Dell ram. [URL] PS for older optiplex in ddr3/ddr2 gen, any non ECC desktop ram that is not too fast would do.
I bought pc June 2020 and ive only turned it on now, (I didnt need it as I thought,so i decided to keep it) Disc space is 100% and Mem is 80% I cant get it to run smoothly. It works fine if i only use internet, when i use a program like photoshop it just freezes up. Ive reinstallled windows and got all updates but no change Warranty is up and Del dont seem to interested. Id appreciate any assistance.
Memory and Disc 80- 100% Optiplex 3070