@central4allgmail-com,

Have you backup your database before starting the migration process? If so, please restore it and start the process again. 

You mean the DB of the site with wpforo ? or the old one?

i believe you mean the one with wpforo

Have you backup your database before starting the migration process? If so, please restore it and start the process again. 

Also, please note when it stopped, for some reasons you just need to press F5 on this page. 

which tables should i clean first to start the migration from scratch? to avoid the duplicates.

1) I started the transfer and from my mistake, it stopped what should i do now?

Delete everything that was moved?

Or just start it again?

2) In a big server, what settings for transfer would you set?

I mean how many users to migrate at once,etc

Please note, that user passwords will be preserved if you migration from WordPress plugins like bbPress, Simple:Press, Asgaros or from any Q&A forum plugins, because user passwords hashing/encrypting algorithm stays the same with WordPress functions. However, if you migrate from stand-alone forum software like phpBB, SMF, MyBB or Kunena there is no way to preserve passwords. The password hashing/encrypting algorithms are totally different and they don't match to WordPress. There is no way to decrypt password hashes, this is one-way encryption process, thus all users password will be changed. Users should reset their passwords using "Lost your password?" link located under forum login form.

You also can add a small note/message to forum users and put the reset password link in that message on top of your forum home page using Admin Note tool in Dashboard > Forums > Tools > Misc admin page.

Please see the screenshot.

Please try to fill the fields as shown in this screenshot:

All  prefixes are "as_"  and there is not exist any that start from "kunena_ "  please look at the phpmyadmin tables screenshot.

http://imgbox.com/OX4hampM