Old Mac high memory use with MS Officemac

+1 NEVER EVER install any of the following types of third party apps on a Mac.

• Antivirus
• Cleaning
• Security
• VPN
• Maintenance

At best 100% worthless and they all have reputations for causing unwanted, buggy behavior. They do absolutely nothing that Mac OS does not already do. Simply locate the developers uninstall instructions for TrendMicro and follow to the letter. It would also be wise to download FindAnyFile (the free version) and have it search for anything with Trend Micro in it and that will ensure it is fully uninstalled. Then restart the computer in Safe Mode and finally restart normally.

Finally, a 2015 is obsolete and it is at the age where you will have a lot of difficulty getting support for your third party apps. It's time to upgrade, consider a new Mac mini and external display. For about $1500 you can have a brand new Mac that will far out-perform a 10 year old HD based Mac, a 1 year warranty, eligibility for AppleCare and not to mention the peace of mind that have have future proofed for years to come.

To migrate from the old machine to a new one, just follow the steps in Setup Assistant and Migration Assistant.

Start by getting rid of trend micro. It will cause far more problems than it can solve.

Tittusmoody wrote:

The Mac wants to update MSOffice, but cannot because of the decision to no longer to support standalone versions.

That iMac cannot run any version of macOS later than macOS 12.* (Monterey).

Microsoft has a policy of supporting only the three most recent versions of macOS – which are now macOS 14.* (Sonoma), macOS 15.* (Sequoia), and macOS 26.* (Tahoe).

Microsoft Support – Upgrade macOS to continue receiving Microsoft 365 and Office for Mac updates

Bottom line you’re running old software on old hardware, neither of which is still supported by their manufacturers. Time marches on.