This is very odd, I do not see any issues, so I took your code and it compiles for me with no errors. But then I noticed your post says you are using engine version 4.11. If you are, that would definitely be your problem. This is current engine code your using. In engine 4.11 the overlap function most likely has a different code signature. I would recommend updating to 4.20 and this should work. If not, you will need to use the 4.11 version of the signature by finding the delegate inside the UPrimitiveComponent class. (Which it looks like the compiler gave you the answer.)
So change your signature for your OnOverlapBegin function in your header file and cpp file to this:
(AActor* OtherActor, UPrimitiveComponent* OverlappedComp, int32 OtherBodyIndex, bool bFromSweep, const FHitResult& SweepResult)