Slow boot because of plymouth-quit-wait.service

I am using PopOS as my OS I noticed that it takes too long to boot-up the reason might be because I use a HDD but, when I was using ubuntu the boot time was faster So, I checked the boot time with

-analyze

command this was the result:

Startup finished in 3.998s (kernel) + 44.094s (userspace) = 48.093s 
graphical.target reached after 44.028s in userspace

then I checked which process makes it slow by using this

-analyze blame

command and this was the result:

29.893s plymouth-quit-wait.service          
 9.881s networkd-dispatcher.service         
 8.984s accounts-daemon.service             
 7.326s udisks2.service                     
 6.843s systemd-journal-flush.service       
 6.358s fwupd.service                       
 5.468s system76-power.service              
 4.872s polkit.service                      
 4.309s dev-sda3.device                     
 4.219s avahi-daemon.service                
 4.138s NetworkManager.service              
 4.123s switcheroo-control.service          
 4.119s thermald.service                    
 4.115s systemd-logind.service              
 4.115s wpa_supplicant.service              
 3.147s ModemManager.service                
 2.954s gdm.service                         
 2.694s gpu-manager.service                 
 2.662s grub-initrd-fallback.service        
 2.523s grub-common.service                 
 2.490s apport.service                      
 2.260s apparmor.service                    
 1.688s e2scrub_reap.service                
 1.612s systemd-resolved.service            
 1.561s lvm2-monitor.service                
 1.296s user@1000.service                   
 1.185s networking.service                  
 1.025s systemd-udevd.service               
  961ms rsyslog.service                     
  892ms systemd-modules-load.service        
  790ms systemd-cryptsetup@cryptswap.service
  724ms keyboard-setup.service              
  623ms systemd-sysusers.service            
  528ms systemd-udev-trigger.service        
  481ms systemd-random-seed.service         
  461ms systemd-rfkill.service              
  426ms colord.service                      
  401ms systemd-sysctl.service              
  333ms upower.service                      
  321ms systemd-tmpfiles-setup-dev.service  
  305ms systemd-tmpfiles-setup.service      
  277ms ifupdown-pre.service                
  257ms dev-mapper-cryptswap.swap           
  251ms ufw.service                         
  182ms systemd-journald.service            
  180ms systemd-user-sessions.service       
  174ms pppd-dns.service                    
  126ms systemd-remount-fs.service          
  104ms systemd-timesyncd.service           
   91ms dev-hugepages.mount                 
   90ms dev-mqueue.mount                    
   89ms sys-kernel-debug.mount              
   88ms sys-kernel-tracing.mount            
   87ms blk-availability.service            
   84ms kmod-static-nodes.service           
   64ms setvtrgb.service                    
   54ms console-setup.service               
   37ms user-runtime-dir@1000.service       
   35ms systemd-update-utmp.service         
   24ms rtkit-daemon.service                
   13ms plymouth-start.service              
   11ms plymouth-read-write.service         
    8ms alsa-restore.service                
    5ms systemd-update-utmp-runlevel.service
    5ms resolvconf-pull-resolved.service    
    3ms sys-fs-fuse-connections.mount       
    2ms sys-kernel-config.mount             
    1ms finalrd.service

-quit-wait.service

is in the top of this list with 29 sec time to finish... Please answer these questions 1. What it does? 2. If it's not necessary than how to disable it? 3. Is there any other unnecessary process in the list that I can remove if yes than how Thanks!