Electric Problems on a 328i

Hey guys I am new on here so I enrolled in college this year and obviously I had to get a car to get there. I ve always been a bimmer fan so I wanted my first car to be a BMW. I basically got the car off craigslist for 2.5k its a 1999 328i with m3 rims clean exterior and interior but the only catch was it needed a new alternator and the drivers window usually jams but nothing to talk about.

Long story short I got a new battery + a alternator off a salvaged bimmer( I had it tested it was good) I installed both of them and the battery still wouldnt charge. Today I had my friend give me a jump start battery was completely dead but he gave his car a bit of gas so it would charge my battery so I got a dc tester tested the battery showed it was charging. The dashboard had the red battery sign before i got the alternator changed now the battery sign just goes away when i start the car. Oh and the car doesnt really run after a jump start it ll probably just move a few feet. P.S the belts are in bad condition bad i mean they still move so before I change anything else I want to know what the exact problem is and the voltage regulator on the alternator is good thats the most information i could think of I d appreciate if any of you guys could help me solve this.