New to Bitcoin and have a question.

So I am brand new to bitcoin and am pretty overwhelmed with the logistics of it. I am particularly concerned with my investments. I will try to explain my confusion the best I can. —So I am concerned and confused about If I invest say 100 dollars. The money I invest fluctuates in value depending on bitcoins value. If bit coins value drops, my investments value will also drop somewhat proportionally. Does this mean that if bitcoin drops a certain percentage, Not all the way to zero, but if it drops just enough, will my 100 dollars invested have no value and be zero? Would I have to reinvest another 100? Or is it a percentage type thing where say if bitcoin drops 50% then my investment will only drop 50 percent. TLDR: If I Can summarize I’m curious if a 50% value drop in bitcoin would make my $100 turn to $50. I hope this makes sense I have a small brain lol.