I hope English is okay here. I used translate to read everything.
I agree that defender and updates are sufficient. Do not disable UAC.
If you want to clean it out occasionally, try Bleach Bit. It basically does everything CCleaner does without messing with your registry.
I used to suggest MalwareBytes, but it needs to be set to not start with Windows. Also, only run it occasionally to clean. It has been falling victim to software bloat as well, so you may get various opinions.
As for you old laptop:
First you may be able to replace the charger. If it is the charging port, sometimes those are modular and can be replaced very easily. My daughter's HP had just a wire to unplug and it came right out. I did use some epoxy putty because the plastic in that area was crumbling.
Second, you can replace the hard drive with a SSD and significantly speed it up. A small 256 GB - 512 GB SSD is relatively cheap.
Lastly, Linux is not as difficult lately. It would be worth it to try, especially now that you have another one to use if you have problems. I think Mint is pretty user friendly, but again everyone has their own opinions.