2019 iMac seems low on memory

My 2019 iMac is struggling and I remember adding more RAM to a previous model. However, the answer to this similar enquiry How to increase my iMac's memory? - Apple Community seems to indicate that this isn't possible and I would be grateful for advice how I can improve it's performance please. I attach all the metrics requested in the enquiry above. Thanks in advance for any guidance.



[Edited by Moderator]