STRING type fields, any risk?

Hello

In our system we have a Z table to store a Z module pool prog., wherein some field's data will is not fixed in lenght, for example, long texts entered by user on Z dialog prog.'s screen, like that we have 5 long text fields on this Z dialog prog., hence initial developer created a 5 fields with STRING data element in this Z table

Pls. let me know

1) is it OK to have 5 fields with STRING type data in the Z table?

2) At this point (users are using already in production since 3 months) can i remediate/repair it any thing?

3) If i leave it as is, going further, do we gonna have any risks/dangers?

Thank you