For the extension Akeeba Backup Core package version 8.3.3 is available, but it requires at least PHP version 7.2 while your system only has 7.0.33-0+deb9u12

For the extension Akeeba Backup Core package version 7.4.0.1 is available, but it requires at least PHP version 7.1 while your system only has 7.0.33-0+deb9u12