how can I make my iMac more faster?
I have macOS Big Sur, 21.5 inch, mid 2014 is too slow, what can I do?
iMac 21.5″, macOS 11.6
Too slow doing what? Generally it is due to a slow hard drive. You can get an external SSD and boot from it.
You might also run etrecheck and attach the full report with the "more text" button below.
The free version is fine for this.