Installing Big Sur - system apps doubled

Hi,
I have a MacBook Air from 2013 and recently installed Big Sur (before that I hade Sierra). In the finals steps of the installment I got an error message but somehow could finish the installment.
However, after that, Safari will not launch anymore at all and also, ALL built in system apps are now double (the Sierra one plus the Big Sur one).
How can I fix that problem / delete the doubles?
Thanks :)
Installing Big Sur - system apps doubled
 
 
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