Tonight I am starting new courses, teaching constantly, and this reminds me to recommend the following to you:
Start using your camera in manual mode (“M”) and with auto ISO disabled. This way you set ISO, Aperture and Shutter Speed. Those are the only three variables that can affect exposure – use them yourself and understand the effects.
You see, if you use automatic modes, these “fight against you”. For instance, increasing ISO will not make your image brighter when your camera is set to an auto mode, since the camera will adjust aperture or shutter “the other way”. But it will not tell you this, leadinf to confusion.
So your exercise for today – and until you understand exposure properly: shoot in manual mode the entire day and adjust everything yourself. This is the only way you will understand photographic exposure.