Permissions mayhem cause iMac app to stop working

Hi all,

recently Ive purchased a new iMac (2019) and created some files, then backed up the HD and carried with me where Ive an older iMac (2015).

When I tried to grab the files from external disk a no entry red dot sign prevented me to access folders and files.

Did some online research and found out that apparently the reason was that the new machine has different user creds.

So I decided to create new user with the same creds as the new machine.

At first nothing changed, then on the advice of nearby apple genius Ive given admin privileges to that new user.

I was ultimately able to access folders and drag the needed files into documents folder within my older machine internal HD.

Now little did I know this would wreck havoc on my iMac.

In the backup files logged as original user we noticed that some of the folders were still locked by that no entry sign, so we restored permissions via get info and giving the folder user access.

Now everything seemed back to normal except, when I login with my original user still get the issue of being unable to open any folder plus now I cant launch any app.

Logged in with new user (same as new machine user creds) I can access folders open some apps, though mac mail quits all the time, and asks to repair permissions within the library however that doesnt seem to cut it. The warning sign keeps popping up and mail quits unexpectedly, the macosx needs to repair Library permissions in order to run apps keeps popping up as well.

Can you please help me? We are in the middle of rolling out some software and cant afford this setbacks.

I need mac mail and to re-establish control of my iMac.