Oracle 18c

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create table your_table (descr) as
select 'Test1 words = 30 have so much words = 20 over 60 words +' from dual
union all
select 'Test2 words = 30 have so much words = 20 over 60 words +' from dual
union all
select 'Test3 words = 30 have so much words = 20 over 60 words +' from dual
union all
select 'Test4 words = 30 have so much words = 20 over 60 words +' from dual
4 rows affected

select * from your_table

DESCR

Test1 words = 30 have so much words = 20 over 60 words +

Test2 words = 30 have so much words = 20 over 60 words +

Test3 words = 30 have so much words = 20 over 60 words +

Test4 words = 30 have so much words = 20 over 60 words +

update your_table set descr = REPLACE(descr, 'words = 20', 'Alpha = 20');
4 rows affected

select * from your_table

DESCR

Test1 words = 30 have so much Alpha = 20 over 60 words +

Test2 words = 30 have so much Alpha = 20 over 60 words +

Test3 words = 30 have so much Alpha = 20 over 60 words +

Test4 words = 30 have so much Alpha = 20 over 60 words +