PC lent (Chrome, explorateur...) pendant copie de fichiers

Hello
 
I have noticed, for some time, that when I transfer files (SSD -> external HDD to USB3) the PC is rather slowed down.
Pages in Chrome load very, very slowly (less slowly with Firefox).  
 
My processor is an i7 10700K, 32GB RAM.  
 
Usage through Task Manager is 13% for CPU, 40% memory and 18% for hard drive...
 
Do you have a lead? This doesn't seem particularly normal to me...