How to parent level Blueprint to c++ script inherited from AActor?

I’ve created a c++ script that contains necessary functions and are visible for BPs (using UFUNCTION() macro). However I need to make several triggers. And when you visit one of them the specific functions are being called. I tried to create a BP-child for this c++ script, but I can’t add OnOverlapBegin() on this BP for specific trigger in the scene. I realised that it is possible to do in level BP. But the functions in c++ script I need are invisible for level BP. What should I do?

Creating a C++ Level Blueprint