does bittrex work like exchange trades if your selling

Exchange trades:
Exchanges act as an intermediary who holds everyone's funds. You place a ‘sell order’ (just as you would place a buy order), stating the volume (amount) and type of currency you wish to sell (eg bitcoin), and the price per unit you wish to sell for.

As soon as someone places a matching buy order, the exchange will complete the transaction. The currency will then be credited to your account.

(but altcoin to btc)

so if you would invest a huge amount in altcoins would it depend on how many people would buy from you?

like for example if you want to cash out does that happen instantly

so i am confused by some things and i know the best way to know the answers to these questions are by investing but at this moment i cant.

so the questions are as followed

1: if you buy altcoins from for example bittrex does that affect the market? like does the price go up from that altc? (just to be sure)

2: is bittrex instant or more like a marketplace, because you can see bids and asks from other people. so do the investors sell it to each other?