This first website gives you useful information about the Debian distributions: https://wiki.debian.org.
This website gives you tips and best practices for the Debian distributions: https://www.debian.org.
This next website gives you a lot of useful tips and best practices from users in the Linux community, particularly for the Debian distributions such as Ubuntu: https://askubuntu.com.
This last website gives you a lot of useful resources on various problems faced by other Linux users for various tasks: https://unix.stackexchange.com.