In the first photo, it seems that you try to install skype as a snap package from the gnome software. You said that you installed skype manually by downloading it, but you didn't say if you got the snap version or the deb version.
From the second photo, I assume that since the repo of skype is there, you installed the deb version.
Given that, the problem is that the repo of skype, as illustrated in second photo, is disabled.
You have to enable it in order to get updates.
For clarification, check my repolist including skype repo:
Skype repo enabled.
NOTE: the skype package in the repo is named
skypeforlinux : Skype package in the repo