Resource 128 GB RAM, 6 TB space, Sql server 2014 enterprise.

Problem: Our DB has few tables including 5 'read only tables' of 200GB(approx) each.
Each of these 5 tables have 5 columns (all columns(varchar 100)).
Each col have repeated strings or values. Two columns (col3 and col4) have approx 3500 unique strings or values that are repeating.

Our only query is 'select col1......(all columns) from table x where col1 like 'searchstring%' or col2 like 'searchstring%' (only two col are queried for OR clause) as these are the only match criteria.

Presently query is taking 1hour to 1.5hrs to return results with present index.
I am wondering if there is an efficient way to get result within 5 to 10 minutes.
Thanks