What to do immediately after informing the journal's managing editor that you are withdrawing your paper submission in their journal? After waiting for 7 months (and counting), I decided to withdraw my paper submission to a particular journal. The reasons are as follows:


The review decision for a particular paper is to be made within six months after they received the paper. However, in my case, it has been 7 months since they acknowledged that they received my paper.
A week before the 6 months of review period, I sent an e-mail to the journal's managing editor about the status of my submission. After 21 days, I did not receive any response. That is why
I sent another e-mail to the journal's managing editor about the status of my submission and I included in the e-mail that If I did not receive any reply for a period of 1 week, I will withdraw my submission.
After 9 days, I still did not receive any reply.


So, I decided to withdraw my paper submission via e-mail.

My questions are: (1) Is my decision correct? (2) What should I do after informing the journal's managing editor that I am withdrawing my paper submission? (3) Shall I wait for the managing editor to acknowledge that he/she received my withdrawal submission e-mail? (4) Shall I submit my paper to another journal?
Your answers Sirs/Mams will be highly appreciated.
Waiting for them seems like a lost cause. Unless you have signed some release or given them copyright, the paper is yours. You can submit it as you like. 

But submitting it minutes after notifying them of a withdrawal might be hasty. A few days wait is suggested. But they don't seem to have a very good record of corresponding with authors.