How to persist a lot of Entities with Quarkus?

I wrote my first Playground Backend with Quarkus, unfortunetly the persist perfomance of many objects is in my code very bad.

What I do is

List<CustomerDto> customerData; // Size 100.000
customerData.parallel().forEach..
 * map to Entity
 * CustomerEntity.persistFlush

This takes a lot of time. And looks like very bad code.

What is a good way to store a lot of List<CustomerDto> customerData;