when installing ssh waiting for cache lock code example

Example 1: E: Unable to acquire the dpkg frontend lock (/var/lib/dpkg/lock-frontend), is another process using it?

sudo lsof /var/lib/dpkg/lock
sudo lsof /var/lib/apt/lists/lock
sudo lsof /var/cache/apt/archives/lock

Example 2: why upgrade ubuntu then frequently shows this message "It iwating for cache lock: Could not get lock /var/lib/dpkg/lock.frontend.

It iwating for cache lock: Could not get lock /var/lib/dpkg/lock.frontend.