How drop unused column with dbms_redefinition in Oracle database?

I don't really understand how to delete columns using the dbms_redefinition utility. All the time there are some strange errors and data overwriting. Disabled foreign keys appear in other tables and are not deleted. Indexes are duplicated... If anyone understands how to use this utility, then please help. I would also like to hear about the pitfalls, if there are any and an explanation of each step

I use the following sequence:

1. First, I mark the columns in table A as unused (ALTER TABLE A SET UNUSED (...))

2. Generating DDL to create a new table without unused columns (SELECT DBMS_METADATA.GET_DDL('TABLE', 'A') FROM dual) and create table A_temporary

3. And finally I use dbms_redefinition:

   DECLARE    p_owner    varchar2(30) := 'user';    orig_table varchar2(30) := 'A';    int_table  varchar2(30) := 'A_temporary';BEGIN    DBMS_REDEFINITION.START_REDEF_TABLE(p_owner, orig_table, int_table, NULL, dbms_redefinition.cons_use_pk);END;/DECLARE    p_owner    varchar2(30) := 'user';    orig_table varchar2(30) := 'A';    int_table  varchar2(30) := 'A_temporary';    num_errors PLS_INTEGER;BEGIN    DBMS_REDEFINITION.COPY_TABLE_DEPENDENTS(p_owner, orig_table, int_table, dbms_redefinition.cons_orig_params, TRUE, TRUE, TRUE, TRUE, num_errors);END;/SELECT OBJECT_NAME, BASE_TABLE_NAME, DDL_TXTFROM DBA_REDEFINITION_ERRORS;DECLARE    p_owner    varchar2(30) := 'user';    orig_table varchar2(30) := 'A';    int_table  varchar2(30) := 'A_temporary';BEGIN    DBMS_REDEFINITION.SYNC_INTERIM_TABLE(p_owner, orig_table, int_table);END;/DECLARE    p_owner    varchar2(30) := 'user';    orig_table varchar2(30) := 'A';    int_table  varchar2(30) := 'A_temporary';BEGIN    DBMS_REDEFINITION.FINISH_REDEF_TABLE(p_owner, orig_table, int_table);END;/DROP TABLE A_temporary CASCADE CONSTRAINTS PURGE/

I took this instruction from here. Is everything okay in it in the three steps that I take and I shouldn't have any problems, or am I using it incorrectly and you have any comments?

P.S. The table I'm doing this for has a lot of relationships with other tables and takes up a lot of disk space (about 200 GB)