I do not understand yay output

It is saying this now …

yay -Syyu                                                 ✔  6s  
:: Synchronizing package databases...
 core                  166.2 KiB   684 KiB/s 00:00 [######################] 100%
 extra                1889.5 KiB  3.35 MiB/s 00:01 [######################] 100%
 community               7.0 MiB  6.48 MiB/s 00:01 [######################] 100%
 multilib              174.0 KiB   644 KiB/s 00:00 [######################] 100%
:: Starting full system upgrade...
 there is nothing to do
:: Searching databases for updates...
:: Searching AUR for updates...
 -> Missing AUR Packages:  kvantum-theme-matchama
 there is nothing to do

Your system is up to date.

You have a local installed package kvantum-theme-matchama which doesn’t exist in the repositories nor the AUR.

The output of yay isn’t really a concern - please read

I have not installed much manually. This is almost a clean install.

Then it can be a package that has been dropped from Manjaro repositories.

//EDIT: seems like it is exactly that kvantum-theme-matchama

What should I do now? Remove that package??

Yes! Also see:

Then it was probably installed as a dependency for another package some time in the past. Check your orphans and possibly remove unneeded ones.

Do you use it? If you don’t use this theme package then remove it yeah.

No I don’t and I have removed it. Thanks everybody