"Syntax error: Unterminated quoted string"

The line with

DROPBOX="/root/Dropbox/Backups

does not have a " at the end.

The MYSQL, MYSQLDUMP and GZIP variables refer to the programs used to execute various commands. So they should contain the path of those programs:

MYSQL="/usr/bin/mysql"
MYSQLDUMP="/usr/bin/mysqldump"
GZIP="/bin/gzip"

You can use the output of which <program name> to see what to put there:

$ which mysql
/usr/bin/msql
$ which gzip
/bin/gzip

I faced the same issue as seen below.

MY_VAR="123"#comments

then I put a space before # character, then solved.