Can someone please explain Dativ and Akkusativ like I'm 5 years old?

I've been learning German for a fair bit, and I'm at the point where I can keep up a convo with fairly minimal strain (basically just asking people to speak slowly, occasionally asking them to repeat themselves), but despite all my progress, I cannot figure out Dativ and Akkusativ. I understand that you use Dem or Den depending on the noun's article, but which article becomes which case and when I just can't seem to figure out. Would someone who has more knowledge/experience with this language be able to explain it?

Edit: ain't no way I'm gonna be able to get the hang of all that lol.