When I am trying to login wp-admin then showing this error:
"There has been a critical error on your website. Please check your site admin email inbox for instructions.
Learn more about debugging in WordPress."

Ohh yeah, Problem Solved
deactivate all the plugins using this method

reset your plugins folder via FTP or the file manager provided in your host’s control panel. This method preserves plugin options but requires plugins be manually reactivated.
#
Via FTP or your host’s file manager, navigate to the wp-contents folder (directory)
Via FTP or your host’s file manager, rename the folder “plugins” to “plugins.hold”
Login to your WordPress administration plugins page (/wp-admin/plugins.php) – this will disable any plugin that is “missing”.
Via FTP or your host’s file manager, rename “plugins.hold” back to “plugins”

After that activate plugin one by one

Sounds like a perfect time to review, vet, and determine, which (if any) plugins are actually required. Give yourself time on each step (at least two weeks) before adding another, else you will get conflicting signals or might not know which one has a "slowing" effect or other adverse properties.

Glad you solved it! The more we do for ourselves, the better our knowledge down the line!

Hello Mr. tangor, I need your help,

A few months ago I have uploaded a new small website of 20 pages at that time I forgot to delete a folder and folder name is "revision". The folder was of another shopping website, In the folder have a .php page that was redirecting my website to another website pages. https://www.example.com/revision/index.php?id=996435
https://www.example.com/revision/index.php?id=986637
https://www.example.com/revision/index.php?id=987534
https://www.example.com/revision/index.php?id=989934
https://www.example.com/revision/index.php?id=990534
https://www.example.com/revision/index.php?id=991236 -------------these are 800+ pages.

On my website only 20 .html pages but now webmaster is showing 833 Valid - Indexed, not submitted in sitemap.

Now I have deleted this folder and set 301 redirection with 404 page. Errordocument 404.html

I think these pages are hurting my SEO, should I need to disavow these pages or use google URL removal tool?

please help me, I am very confusing.

[edited by: phranque at 11:03 am (utc) on Dec 6, 2019]
[edit reason] exemplified domains [/edit]

If your redirects are all correct you will just have to give it time.

Secondly, search engines NEVER FORGET a url they have visited and will continue to ask for it (them) for decades! Have the correct response, 301, 403, or 404. I lean toward the latter, after all, the page no longer exists. :)

If you want to speed things along return a 410 (gone) and move on to doing other things to improve your site.

Pages do disappear from the web. EVERY DAY.