Guest posting is the best way to go through. For the easy things, I have just posted 5 example links here, https://www.seoforum.com/thread/blog-post-rules.

do you have any advice about which websites that are free and easy to write something in order to have backlinks

Yes, the Medium set it so. You can find more information here, https://medium.com/new-writers-welcome/new-writers-crash-course-1-how-to-get-indexed-on-medium-dca736e76be5

what is interesting that i can see just one backlink which is from medium on google search console. And why the blog articles that i wrote on medium are onfollow, nofollo...

You can google for it and make your own list. Alternate way to prepare your own list is, follow a competitor's backlinks. Here are a few for you, www.vingle.net www.soope...

Using the Google Search Console, submit manually for removal of those invalid pages from cache and index.

Hi Binayjha, Thanks for the reply. Could you please send me few if you have? Thanks. Kind regards, Sam

Update some content on the page, text/ image/ video or whatever content you can update. Also, get 1-2 good backlinks. Things will settle with better outcome.

Go to, Google Search Console >> Removals >> New Request and then remove those URLs...

You should ignore these and find some better content publishing sites.