Missing background image setting in admin of twenty nineteen

It’s not present because it’s not supposed to be present, it was removed.

While originally added to the theme, it was deliberately removed due to accessibility concerns, see https://github.com/WordPress/twentynineteen/issues/708 which is the same question but on GitHub

Keep in mind that the video you linked to is not the final version of the theme, but a WIP version mid-development prior to its final release

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)