I installed Ubuntu 16.04 LTS, and I would really like to download stuff like Unity Tweaks to customize everything. Every tutorial shows you to just go on Ubuntu Software, and search for Unity Tweaks and tadaa. Done.

But when I go in there (and yes, in on the All tabs) I just see a few Apps previewed, like Skype, subsurface, slip, sublime text and 3 others. In the list "Editors Picks". I don't have anything else. And the biggest problem is when I type in Unity Tweaks to find it, it just tells me "No Application Found". When I only search Unity it finds some other Apps called Unity, but it's all not what I want. It looks like the Ubuntu Software contains like 10 Apps and that's it??