Since my application took a long time to give any update since DM, I did few things and I will share them here, so anyone in my situation can try to do them.
1. I called several times to IRCC call center: I did not get any help from them. They just said everything in your application seems good. You have to just wait until you get your COPR (So I don't recommend calling the IRCC call center)
2. I sent a general web form (without attaching any document): That doesn't do any help either. I got a general reply by saying they are taking a longer time than usual due to covid-19.
3. I obtain a GMCS note: GMCS note is really valuable, I can see every step that they have done regarding my application.
4. I sent a case-specific enquiry through webform ( I attached my son's Canadian birth certificate because I saw in the GMCS note that they have raised a comment on why I haven't included my son in the PR application): That may be helped because I got a reply that they have forwarded my son's birth certificate to the officer. I suggest, if you are sending a web form, attached documents such as your current work permits in Canada and/or documents to prove that you are in Canada.
5. I contacted PM: Since I did not get any update for more than 6 months since DM, I called to Ministry of immigration and they gave me the local PM's (parliament member's) number and asked me to contact him. So I contact his assistant and she sent me a consent form. Then she told me that, they have contacted the IRCC regarding my application and you will get an update soon. And here today, I got the email to access the Permanent residence confirmation portal.
Thus, from all my experience, I would say the effective way to speed up your application is to contact the local PM (parliament member) and they will help you to get your PR soon.