Selections going wild
When I choose a Quick Look at a file by employing the space bar. a blue line appears around the window and instead the item is opened in its application.
And if I try to rename something that blue line shows up again.
It will be helpful to know exactly which Mac model and year is your computer. And which macOS version you are running. Without that info it will be more difficult to assist. Find that info by clicking the Apple menu () at the top-left of your screen and then select About This Mac. (Note- for privacy and security reasons, please never post your serial number.)
Meanwhile, have you restarted your Mac?
If a simple reboot of your Mac doesn’t fix things, see if the problem still happens in safe mode.
How to use safe mode on your Mac - Apple Support
Safe mode will often correct weird software behavior by forcing the OS to do disk repair, clear caches and other housekeeping and disables acceleration and third-party mods. When you're in safe boot, the machine won’t be at its best performance, especially with graphics, but that's expected.
Does the same thing happen while in Safe mode?
You can exit safe mode by restarting your Mac normally.