Activity monitor CPU high.

High memory usage jumps out some of which is from Firefox. This might be of some help.https://support.mozilla.org/en-US/kb/firefox-uses-too-much-memory-or-cpu-resources Try doing a SMC reset and see if your CPU and Memory usage goes down.

How to reset the SMC of your Mac - Apple Support

Make sure all software is up to date including any third party. Just to be safe check your hard drive.

https://binaryfruit.com/drivedx You may need anew battery in the future.

Other than that I don't see anything that jumps out at me.

That doesn't really show anything as there are no values to check. Do you see any apps in activity monitor that are using a large portion of CPU. Are you running any a system cleaners like CleanMyMac or any antivirus programs. If you do, look up how to uninstall then and do so. To help check your computer. Download and run Etrecheck. Then post the system report.

https://etrecheck.com/

Your Etrecheck report was not a complete report. Go to system preferences Security & Privacy Click the lock , go to privacy and in left column click on full disk or disk. the in the right box click the + then use applications to click on Etrecheck to give full disk access. If Etrecheck is not in the applications folder move it there.