It’s a space where everyone can upload apps. Same like aptitude.
Yeah, you could, but you mustn’t have. Have a look on your phone if something unknow happens or if your data transmission get higher and higher. If here is nothing crazy, your are on the bright side of life.
You can check your apps with ClassyShark3xodus for unwanted tracker and with NetMonitor you can check which remote IP is used by your apps. both you can get at f-droid.