On Ubuntu 14, I used to always use Ubuntu Software Center to find and install programs, plugins etc. You could easily find anything by typing the name in the search bar. But now in Ubuntu 16.04 things don't work like that anymore for some reason... It doesn't find any programs other than I already have installed (not even GIMP or Adobe Flash Player...).
And when I try to install program from website by opening it by default in Ubuntu Software it gives me the message: "failed to open". Can anyone help me out here? How can I install programs on Ubuntu 16?