Welcome to the Manjaro Community! 
You need to remove (or at least add a # to the beginning of) the [community] lines in /etc/pacman.conf. Usually that and one or two following, before the next blank line.
sudo nano /etc/pacman.conf
This is documented in a Sticky at the top of the Updates section:
There will likely be a number of other files which need to be tended to. Please post output of:
pacdiff -o
… and select the pasted output, then click the </> button at the top of the reply window for proper Forum formatting.
This may also be helpful:
NOTE: Edited as I posted incorrect commands first time. 