I ran the commands systemd-analyze blame and systemd-analyze critical-chain. I found that dev-loops are data needed to load snap-installed programs quicker and plymouth stops when everything stops (so it doesn't slow boot). It also prompts me to type password before I login, something wasn't happening before.
Edit: I also deleted all snaps, still nothing. I noticed at startup it shows receive error ,pci error, bad tlc .Although I googled it and didn't find anything to solve this problem.
Here's the output of the commands :
systemd-analyze blame
20.726s plymouth-quit-wait.service 5.084s bolt.service 2.435s dev-nvme0n1p1.device 1.454s snapd.service 1.301s dev-loop21.device 1.280s dev-loop20.device 1.270s dev-loop16.device 1.267s dev-loop22.device 1.264s dev-loop17.device 1.263s dev-loop19.device 1.262s dev-loop18.device 1.258s dev-loop24.device 1.252s dev-loop15.device 1.238s dev-loop23.device 1.236s dev-loop25.device 878ms dev-loop14.device 781ms systemd-rfkill.service 526ms dev-loop13.device 420ms dev-loop12.device 335ms systemd-journal-flush.service 312ms dev-loop10.device 311ms dev-loop11.device 280ms dev-loop7.devicesystemd-analyze critical-chain
graphical.target @21.754s
└─multi-user.target @21.754s
└─snapd.seeded.service @2.173s +279ms
└─snapd.service @717ms +1.454s
└─basic.target @693ms
└─sockets.target @693ms
└─snapd.socket @691ms +2ms
└─sysinit.target @688ms
└─systemd-backlight@backlight:intel_backlight.service @3.006s +15m
└─system-systemd\x2dbacklight.slice @3.005s
└─system.slice @115ms
└─-.slice @111ms
Here's my SystemdAnalyzePlot.svg:
