Beautiful dark theme for Linux Mint Cinnamon Zorin OS Dark Theme with Tela icons https://github.com/vinceliuice/Tela-icon-theme
Open File manager choose view and select Show Hidden Files
Extract Cinnazor Zip File and Place to /home/.themes
Extract Tela icons Zip File and Place to /home/.icons
Go to preferences > Themes select Cinnazor
For transparent File Manager, you have to install nautilus file manager
sudo apt-get update -y
sudo apt-get install -y nautilus
Then Go to Preferences > Preferred Application
Choose different file manager
or copy and paste code below to terminal
xdg-mime default nautilus.desktop inode/directory