I was running into trouble trying to update my Manjaro on my MacBook Pro today, I kept running into package conflicts which could not be resolved. Pacman suggested deleting certain packages but the delete would not complete because of dependencies. So the issue was how to resolve dependencies in Manjaro and how to remove unwanted packages.
After a bit of reading I found a useful tip. Most of the packages that were causing conflicts on my install were actually no longer needed. After some searching I found a way to quickly check for and remove unused or orphaned packages in your Manjaro install. You have to run this command as root:
# pacman -Rns $(pacman -Qtdq)
This command recursively finds and gives you the option to delete all orphans and their configuration files. It found 87 orphans in my Manjaro install and once they were removed I was able to update my install with no sorrows.
Note that if no orphaned packages are found, Pacman will return the message:
error: no targets specified
Hope this is helpful.