You might have to check the condition of the injector/ejector mechanism, or the control servo may have become damaged or misaligned. If you can't fix it yourself, it might be just as cheap to find another tape player from eBay, or a local junkyard.
In your high school years, get good grades in math and science, namely Chemistry, Biology, Physics, History, and Mathematics. You would want to excel at these courses in order to...