Anything like this will do well for you (for the reliable 1TB hard drive):
WD Blue 1TB Desktop Hard Disk Drive - 7200 RPM SATA 6 Gb/s 64MB Cache 3.5 Inch https://www.amazon.co.uk/dp/B0088PUEPK/ref=cm_sw_r_cp_api_T-DRybYDV38PS
There's your answer then. It seems like your hard drive has failed as the write speed is basically unusable. Try getting a cheap hard drive (100gb will do fine) and put arma on it to see if it fixes the issue, if it does fix it, I would reccomend getting a decent 1TB+ hard drive which is reliable.
What is the write speed of the hard drive (found in the task manager) @DSGT Yak
Also did this start happening after a specific update or just randomly?