I did a Google search for Youmi/A!Gen and eventually got to Youmi.A which is described as adware, which is rather what I suspected. F1.apk seems to be the installer for the F1 Challenge game. On balance, I think you've somehow got this (as part of another download/install??) and that it's installed itself as a system file, which is why you can't get rid of it. I also think that the adserver stuff is built into it (and isn't located elsewhere), which is why Protect is picking it up. It's not exactly a false positive, but the fact that Avast ignores it suggests that some signature files regard it as a threat and some don't.
On balance, as long as you don't execute the file, I think you're OK. Do try having another go with the phone connected to a pc, showing system as well as hidden files. If you find it, see if you can change the attributes (non-hidden, non-system) and if you can then delete it, either with the pc or with ES File Manager.
