When your sell order is higher than the highest bid it will be put onto the order book. If your buy order is lower than the lowest ask it will be put onto the order book.
You can sell or buy instantaneously by fulfilling an existing order. When you do a market order the exchange automatically presents you with the most favorable order. Once that favorable order is gone it will take the second most favorable order and so on. Each new order is less favorable than the last one.
By repeatedly selling Bitcoin you are clearing the order book on the buy side. Less buyers mean lower prices.
If a buyer then comes along who's willing to pay that price—and that price is higher than the current market price for the token—then the token goes up in value.
It’s the same story with any currency. Basic foreign exchange concepts.
I guess you're describing a situation where Bitcoin is used purely as a store of value and never as a medium of exchange. I can agree that a fiat store of value, if never used as a medium of exchange, or even a numeraire, is on very shaky ground.
Again, in real/practical world merchants are not there to invest in crypto, they are there to produce tangible goods and collect surplus of exchange tokens —- everything that is not profit needs to be de-risked.
That's a misunderstanding of how these things work. If selling drove the price down, then the price would never go up! Why? Because nobody can buy without a sale on the other side of the transaction. The common belief that selling lowers the price comes from the fact that if you put out a big sell-now order on a market, it will eat through the asks sitting there already. However in the slightly longer term others will put up new asks, up to the equilibrium where the price is close enough to the perceived value that there's no money to be made, after tax, by going in to move it closer. The phrase "Sell! Sell! Sell!" is based on the idea of selling at any price because you want to get rid of it so badly, but that's not a normal sale. That only happens when a party suddenly realizes that they have too much of something, not when they are doing everything as expected.