The gold standard for ear training is sight singing solfeggio since you are required to produce the pitches in your head. However this requires a knowledge of standard notation.
Before undertaking sight singing it is a good idea to work on all intervals in both directions as well as harmonically, up to an octave as well as being able to find the tonic of a given excerpt. Finding tonic can be tough in some situations since music is often written as to obscure the tonal center as a way of creating a dreamy feeling of uncertainty or dissonance.
Rest assured you can develop your skills. I took ear training classes in college and while it wasn’t a strong point for me, I certainly improved and am more than proficient currently. Some useful programs are Auralia or Macgamut. Do not be afraid to start very basic, a strong foundation is important. The most important thing is consistency. It takes several years to master these skills. Best of luck