Three quick comments:
1. Don't put single quotes around your PL/SQL blocks. For example, I don't know why you have a single quote after AS and another one after END.
2. In setting variable SQLSTRING you should use single quotes, not double quotes, and you should not have a semi-colon inside the assignment (unless you are assigning a DDL block with BEGIN/END statements.) For example, change it to read sqlstring:= 'INSERT INTO Looking VALUES (' || car || ', ' || person || ')';
3. What is the LANGUAGE stuff at the end?