Do you lose your property when you file Chapter 7?

Hardly ever. In Chapter 7, the Court is not interested in your property except to the extent that it has equity in it… that is, to the extent that it is worth more than what you owe on it. (To the extent of any lien on it, it really belongs to the creditor. Thus, the value of your property is important). You are allowed to protect (“exempt”) your equity in property up to certain dollar limits in different categories of property, such as in your residence, your automobiles, your household goods, etc.
The vast majority of Chapter 7’s are “no asset” cases where nothing is lost or surrendered. If you have substantial equity in something, you would want to bring it up and discuss it with the lawyer before you file to see if it might cause a problem. If you are subject to losing something in Chapter 7 that you don’t want to lose, then Chapter 13 may be your best option.