Audi

Before it died, it was idling very low, and it shut off a couple times while waiting at a stop light. I bought it from a private party about a month ago, and the radio did not work. I know audis have some electrical issues…could this be related?It shut off on the freeway the last time I drove it-I quickly turned it back on, and then the turn signals started to blink very rapidly. I tokk it home, and it did not start since. I replaced the battery because the old one was definitely shot, but it still won’t start . When I turn the key in the ignition, it just briefly makes a rough whining sound, and thats it. Could the battery be in wrong? Help! I am running out of money to fix this car! Thank You!