Well, I beleive the best tool for fixing a computer is simply the on off switch!

I think the best way is to find a computer nerd :D

I'd like to say that I am one too, but even then, I still ask other computer nerds for help :)

I think there are computers that are just not fixable. Unless you have a Mac computer you will always be in some kind of trouble, believe me. So go get a good one.

What are Bottleneck Calculators even for? How can they bust my computer? How much do such programs cost?

I have also encountered bottlenecks, but I quickly found how to fix it, here is a useful link https://computerity.net/reviews/best-bottleneck-calculators-for-pc/ . A CPU bottleneck occurs when the central processing unit (CPU) is running at full capacity and cannot handle the rest of the system, limiting overall performance. This can manifest itself in a variety of ways, including: low frame rates in games or other graphics-intensive applications, poor performance and responsiveness of applications, longer load times for large files or programs, high CPU utilization, and high temperatures.