Your food comes up to temperature while cooking, but taking it off the heat doesn't mean the food itself isn't still cooking, you have to account for this, food keeps cooking out of the pan. On a side note this is why it's easy to overcook eggs.
Knife skills are one of the most important things in the kitchen, keep your knife sharp because you want to put as little extra pressure to cut things unless you want to slip and cut yourself. A dull knife is much more dangerous than a sharp one.
You literally, scientifically cannot overcook mushrooms.
Baking is not the same thing as cooking, cooking is an art, baking is a science, baking you cannot fix, cooking can always be fixed.
Spices, they're the thing that holds your dish together, this one is more of an experience thing, the more you cook the more you realize what spice goes in what style of dish, and how they work together. Don't worry too much about this, just find some simple recipes, and follow them, you'll understand it soon.
Lastly, here's a couple phrases or terms people will say in cooking videos that may help to remember.
Fond: the burnt-on stuff that accumulates at the bottom of a pan.
Deglaze: Deglazing is the act of adding a liquid and gently boiling or stirring the fond free from the bottom of the pan to incorperate into a dish.
Roux: A roux is a mix of butter and flour in equal parts often used to thicken sauces and stews, yes, you can combine the two things above with this, to make a better tasting roux, this is how they make some gravies.
Simmer: A small gentle boil that often means small bubbles on the edges of the pan to small bubbles in the middle of the dish, this generally occurs at around 180 degrees.
Shortening: Any fat that's solid at room temperature, that can be incorperated into dough or pre-baked goods to give a crumbly texture. Such as Lard / Monteca (If you live in the south), Butter, or Margarine.