While upgrading the CPU is possible, are you sure that’s the reason?
Often times I find the storage (HDD and/or SSD) is the root issue. As an example a HDD over time gets it’s files fragmented, more so when the drive is 2/3rds full. For SSD’s need more free space so they are able to do wear leveling. A too full SSD will get bogged down as it needs to be more aggressive moving older data to more worn blocks to free up the less worn blockS they where using for the newer data.
Then we have Apples Fusion Drive which is even more complex as the SSD is used to cache so a worn drive can make the system crawl!
So… what is your current drive/s? Also what is your RAM size.
crwdns2934105:0crwdne2934105:0
crwdns2934113:0crwdne2934113:0
crwdns2915270:0crwdne2915270:0
crwdns2889612:0crwdne2889612:0
2