Downloading snapcraft error

I wanted to install spotify and it's not in the application center so I found i can do it via snapcraft and I tried to install it by following this steps ( https://snapcraft.io/docs/installing-snap-on-elementary-os) but then i got this error. And i don't know what to do. I want to have spotify

 

Alright, so your issue is the lock file. I see you were attempting to 'su' to fix the problem but instead you FOR SURE should use 'sudo' instead. Run

Code (Text):

sudo apt --fix-broken install

then enter your password. ALL commands that include installing packages (APT) need to be ran as root. The reason the 'su' command failed is that the root password wasn't set.

Code (Text):

sudo passwd root

.

 

install spotify on flathub website https://flathub.org/apps/details/com.spotify.Client

 

I have gotten the very same error for about three months now. Before that everything worked perfectly. Something must have changed in the configuration of the snap store. Very frustrating.