Hi, I have installed a cursor theme (Protozoa-Blu), but, when I open some applications, the new cursor change. The folder of new cursor is in the folder "Documents" of my account. My OS is Manjaro. What I must do?

moved to Appearance & System Customization

so the cursor works fine in general?
but there are certain apps which show the earlier defaulted to cursor?
specifically what apps are problematic?

you could try installing using the "get new theme" in systemsettings instead of installing from file but it maybe a cache issue so after logging out of your session (you need to do this logged out of your session) remove /var/tmp/kdecache-your_user_name.

ps - how did you install it?

If you have only just changed the cursor, you may need to logout and back in again, or restart the affected applications for the new cursor to take effect.