I am not a Fedora user, but I assume that writing "dnf install Gtk*" is supposed to install all packages whose name begins in Gtk.
Unfortunately some can't be installed together, because they have conflicting dependencies requierements.
In this example it seems that you cant have both GtkAda-2.252-20 and GtkAda3-devel-3.14.2-1 installed, so you need to choose which one you want.
I am wondering: what do you really want to install? I doubt that you really need all
70 packages whose name begins in Gtk.
Also, this thread would better fit in the
Fedora forum where you would find more accurate answers, as both the dnf tool and the packaging of Gtk* are specific to Fedora.