How to reduce BOOT time in Gnome 16.04 [duplicate]

Question

laptop is dual booted with win10 alongside Ubuntu Gnome 16.04 specs- 8 GB ram, i5 5th gen processor,1TB HDD when run -- systemd-analyze blame output shows that first two are taking almost 40 seconds, how to solve this?? (I tried using BUM but no satisfactory result :( )

     20.979s plymouth-quit-wait.service
     19.925s systemd-rfkill.service
      8.710s snapd.refresh.service
      7.036s accounts-daemon.service
      6.428s NetworkManager-wait-online.service
      5.941s dev-sda8.device
      4.731s systemd-fsck@dev-disk-by\x2duuid-4694\x2dE125.service
      4.495s NetworkManager.service
      4.478s ModemManager.service
      4.152s mysql.service
      3.693s grub-common.service
      3.274s apport.service
      3.274s irqbalance.service
      3.221s networking.service
      2.983s systemd-logind.service
      2.924s pppd-dns.service
      2.923s systemd-user-sessions.service
      2.861s alsa-restore.service
      2.856s gpu-manager.service
      2.855s rsyslog.service
      2.854s iio-sensor-proxy.service
      2.774s snapd.firstboot.service
      2.518s apparmor.service
      2.460s thermald.service
      2.325s polkitd.service
... continued