High kernel_task issue on my MacBook Air

My MacBook Air has been such a reliable laptop up until very recently where it has suddenly slowed down and become laggy to the point it is not useable. I have tried deleting 3rd party software, deleting files and cleaning the dust off the fan but nothing seems to work.

I ran etrecheck but do not know how to interpret the results. Is anyone able to please help interpret this for me? Thanks so much

EtreCheckPro version: 6.8.4 (68040)

Report generated: 2024-02-21 11:28:43

Download EtreCheckPro from https://etrecheck.com

Runtime: 43:38

Performance: Poor

Problem: Computer is too slow

Description: 

suddenly very slow and laggy, frequently see the beach ball

Major Issues:

   Anything that appears on this list needs immediate attention. 

   No Time Machine backup - Time Machine backup not found.

   Battery failure - Your battery is reporting that it needs to be serviced.

   Adobe Flash Player installed - Adobe Flash Player is installed on this computer. This is a security risk and no longer supported.

Minor Issues:

   These issues do not need immediate attention but they may indicate future problems or opportunities for improvement. 

   SSD too slow - SSD is showing poor performance.

   High battery cycle count - Your battery may be losing capacity.

   Unsigned files - There are unsigned software files installed. These files could be old, incompatible, and cause problems. They should be reviewed.

   Vintage hardware - This computer may be considered vintage.

   Kernel extensions present - This computer has kernel extensions that may not work in the future.

Hardware Information:

   MacBook Air (13-inch, Early 2015)

       Status: Vintage

   MacBook Air Model: MacBookAir7,2

   1.6 GHz Intel Core i5 (i5-5250U) CPU: 2-core

   4 GB RAM - Not upgradeable

       BANK 0/DIMM0 - 2 GB DDR3 1600 

       BANK 1/DIMM0 - 2 GB DDR3 1600 

   Battery: Health = Service Battery - Cycle count = 896

[Re-Titled by Moderator]