Saving the World Starting as a Slime

The only downside is that both the protagonist and the villain are too stupid.

Treasure Book

The reason I'm only giving you a partial answer is because several of your chapters are inserted from other novels. Why would other novels insert themselves into this one? It makes it impossible to read those chapters and the content doesn't match up.

The main character is too dim-witted; he clearly senses danger but acts as if he doesn't. But the rest is quite good.

Yes, you can watch it. It's a simplified version of "It's perfectly reasonable for a slime like me to easily defeat a dragon, right?"

It made me feel stupid...

The supporting character Li Shao is portrayed in a way that's not just ordinary, it's a bit outrageous. He serves as the villain's lackey while simultaneously provoking the protagonist, acting arrogantly and completely lacking in common sense.

Simplified version: A bunch of dim-witted kids playing together with a self-important protagonist.