How to install Elementary OS Files App.
Install dependcies:
sudo apt install -y libaccountsservice-dev libgdk-pixbuf2.0-dev libgranite-dev libgtk-3-dev liblightdm-gobject-1-dev libwingpanel-2.0-dev libx11-dev meson valac libmutter-2-0 libmutter-2-dev libcanberra-dev libcloudproviders-dev libdbus-glib-1-dev libgail-3-dev libgee-0.8-dev libglib2.0-dev libnotify-dev libpango1.0-dev libplank-dev libsqlite3-dev libunity-dev libzeitgeist-2.0-dev libhandy-0.0 libpackagekit-glib2-dev appstream-util
Update the system:
sudo apt update
sudo apt upgrade
sudo apt dist-upgrade
Then in terminal type:
cd
cd Downloads
wget https://github.com/elementary/files/archive/master.zip
unzip master.zip
cd files-master
meson build --prefix=/usr
cd build
ninja
sudo ninja install io.elementary.files