deleting the records will not free up the space.
you should truncte the table.
if trunctation is not possible, directly try one of these methods

create table new_table as select * from old_table;
truncate table old_table;
insert into old_table (select * from new_table);

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or

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alter table table_name move tablespace < T0_same_tablespace_as_it_was_before >