[MicroStation v8i SS1] deleting elements connected to the base

Mateusz Czajkowski said:

changing the value in msgeo.cfg

It look like you, or somebody else, is using Bentley PowerMap.  What value have you changed?

for others, changing the value in msgeo.cfg to the following resolved the problem:
#----------------------------------------------------------------------------------------
#
#    $RCSfile: msgeo.ucf,v $
#   $Revision: 1.47 $
#       $Date: 2008/12/10 18:00:00 $
#
#  $Copyright: (c) 2008 Bentley Systems, Incorporated. All rights reserved. $
#
#----------------------------------------------------------------------------------------
#========================================================================================
#
#   >>>>> WARNING  WARNING  WARNING  WARNING  WARNING  WARNING  WARNING  WARNING  <<<<<
#
#  This file should never be changed by users! Any configuration changes should be made
#  to specific user configuration files (.ucf) which %include this file. See mytown.ucf
#  for an example workspace which %includes this configuration file.
#
#========================================================================================
%if !defined (BENTLEY_POWERMAP)
    BENTLEY_POWERMAP = 1
    %if exists ($(_USTN_APPL)msgeo.cfg)
        %include $(_USTN_APPL)msgeo.cfg
    %else
        %error Unable to locate required $(_USTN_APPL)msgeo.cfg file, exiting...
    %endif
%endif

%if exists ($(MS_GEOCONFIG_DIR)msgeo_appl.cfg)
    %include $(MS_GEOCONFIG_DIR)msgeo_appl.cfg
%else
    %error Unable to locate required $(MS_GEOCONFIG_DIR)msgeo_appl.cfg file, exiting...
%endif

%undef MS_GEOXFM_LOAD_METHODS
MS_GEOXFM_DISALLOW_INFERRED_DBCONNECTION = 1

I'm working a new microstation file. The cells for this new drawing were copied from the reference, which is also a dgn file, but I got this file from an outsider.

Mateusz Czajkowski said:

it is unlocked but shows an error when trying to modify it

That's not normal MicroStation behaviour.  Another app. may be required to manipulate your elements. 

1. What was used to create your DGN file?
2. Are you using another app. on top of MicroStation?

yes it is unlocked but shows an error when trying to modify it: