finder not working

Hi,

I''m using a 2017 MacBook Pro updated to macOS Mojave. Since the OS update Finder has been acting oddly and I can't work out why.

Sometime if I save a file to a folder, then check it is there in Finder, it is not. But if I re-save it it says it is there, and asks if I want to replace it. The file will then show in the folder.

Downloads are showing in the Download folder until I do the same as above

File modified times are updated - so I work on file, save at 12:20, do some more work and resave, time modified is still 12:20, but if I open the file, it is the later version.

Any ideas how I can correct this? It's getting rather frustrating.

Cheers