W: The repository 'https://mirrors.evowise.com/mariadb/repo/10.1/ubuntu serena Release' does not have a Release file.
Remove the repository with serena codename (Mint 18.01), the repository doesn't support the serena codname.
W: Target Packages (main/binary-amd64/Packages) is configured multiple times in /etc/apt/sources.list.d/additional-repositories.list:...
IMO, your order of priority is correct; the Software Manager is a prettier version of Synaptic, more like a Windows store, but without some of the behind-the-scenes features. If possible, you should always stick with the default repos as they're checked by the distro managers, whereas you're putting your trust into an unknown quantity with a PPA.
PPAs give ...
It looks like you're trying to execute /etc/apt/sources.list. Because it is not a valid executable (it's just a regular ASCII text file) and does not have the execute permission, this won't work.
You'll need to use a text editor to modify sources.list, e.g. nano /etc/apt/sources.list.