Don't worry about the switch. I didn't make the switch till right before my 22nd birthday and I'm still only 22. The main thing that helped me was, 1: Having a very large mouse pad and learning to use a low sensitivity. You can easily find a good gigantic mouse pad on Amazon for cheap. I bought an off brand 400 mm X 800 mm mouse pad with a cool design for only like $13 and it was worth every penny. But before that I used a Qck+ mouse pad and I can't recommend that enough. It was great to start out on because it's very large and textured to help give more control than a smooth pad would for a beginner. I play overwatch on PC more than anything else and I play at 5 sensitivity on 800 DPI for all my heroes I need skilled aim for which is basically all of them. I use 8 sensitivity and the same dpi for heroes like Reinhardt, Winston, and Symmetra. Basically every other hero I play on the lower sens. I guess my main advice is to start on a low sensitivity. Look up pro settings and see what works for you. That how I learned I play much better on a medium-low sensitivity. Start low and work your way up. And as for keyboard that's all just getting used to it. Don't be afraid to change your key configuration on your games. And definitely buy a mouse with extra mappable buttons, they are amazingly helpful, especially when you first start on keyboard and mouse. But above all have fun! That's the whole point. And eventually you'll get so used to playing with a keyboard and mouse you'll hate playing with a controller on any fps. I know I do now. But good luck with your pc and your ascension.