Camera taking dark pictures. Do I need to fix my Aperture ISO or what?

Please help. I'm an amateur photographer. Actually, I don't think I'm even there yet. Thing is learning dslr's can be stressful to the point where I've given up on it. I took it back today and we went to the park I was using it in Manual mode, with an f8 aperture and 100 iso. BUT I put up the Exposure compensation to 5.0 it was good because I no longer had dark images. However, now I'm back home using it in aperture priority, and shutter priority mode. The images are black. I'm getting stressed bc I just don't seem to understand what I'm doing wrong. I've tried learning through youtube and the Internet but it's so stressful. Any tips or any videos that can explain to me what I might be doing wrong, will be appreciated. Please Help. I think I have some talent for photography but honestly I don't seem to understand what I'm doing wrong.

Btw I have the beginner's Nikon D3300.

Please Help Me!

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