I’ve created a menu but the visual result looks strange, as you can see. It only shows vertical items with dots (that I can’t remove) nor can it be changed horizontal display.

I suspect that the css is causing this issue.
Would be very happy for advice, thanks in advance.

Try to follow this troubleshooting method that I made: (It's quite general, but maybe it will tell us something.)
Please make sure that all of your Plug-ins and Theme are updated.
Sometimes it isn’t obvious that there is a plugin update available. Go to WordPress Dashboard > Updates and click the Check Again button to be sure.
After you checked that you are really updated to the latest versions, and the issue still occurring:
Please deactivate all your plugins besides Elementor and see if it helps. If it solves the issue reactivate them one by one to find the culprit. If it didn't help, switch your theme (temporarily) and see if it makes any difference.
Please also regenerate the CSS via Elementor > Tools > Regenerate CSS on your WordPress Dashboard,
then make sure that you clear:
your WordPress cache (your WordPress plugin if you have one), your server cache (if you have one. In this case, you can contact your hosting provider).
Please Delete both Elementor free and Pro versions, then reinstall it.

Are you still in need of assistance?