What's the best way to cash out without creating a crash?

For example, lets just say that I theoretically found my seed phrase for my wallet with 179'725 BTC in it.

Now lets imagine that I theoretically had a weird idea in early 2009 and some weirdos hyped it up. I forgot about it for the last 12 years as I was busy. Now lets imagine that I finally found my seed phrase and a way to access my wallet with 179'725 BTC. Now I want to cash out and move it to my bank account. How would I theoretically go on about this safely if I theoretically had this much money in crypto, in theory of course.

As I am 46 years old I am not quite sure how I can pay out a nice chunck without messing things up. Also I want to know what would happen if I pay out. What would happen to the market?