2001 325i DSC BRAKE Lights on?

Hi!
i just bought my new to me used bmw, it is a 2001 325i
it has 135xxx miles
and i have a few problems with it
- the Brake Light is on on the dash, although i have the handbrakes off
- when the car is in idle, or when i start it up it kind of screeching and squealing noise but it runs fine on the freeway
- the airbag light is on, although the car has never been in an accident
my biggest concern is the light on the dashboard that looks like a triangle with an '!' inside it and this triangle is enclosed in a circle pointing counter clockwise
which i found out to be the ASC+T or DSC
and this light usually comes on when i'm braking at low speeds
also, before the light flashes and turns on the car kind of shakes
and this also happened when i was on the freeway and was cruising at 65 mph and the the car just vibrated like krrrrrrgggg and it sounded like something is grinding in the engine bay and i can feel this grinding from the pedals
the the ASC+T or DSC will then start flashing and stays on
the car does this everytime i use it but if i press DSC it does not do this


also there is a slight rumble/ clunk under the center console specially at low speeds (15-35mph)
but seems to smooth out at 60 -80mph but still barely noticable
could it be the CSB and the guibo

i also hear the air pump cranking when i start the car, it then goes away after a while is that normal?
thanks

You need to scan codes with a BMW scanner. That will tell you the exact problem. The screeching noise at startup likely means you need a belt/pulley job. The airbag light is usually lit because of 2 reasons: bad seat occupancy sensor or bad seat belt buckle switch. Again the scanner will be able to tell you what exactly. The SAP should run for a minute or so when you start the car. This is a US only feature for emissions purposes (goddamned green nazis) and is normal as long as you only have an initial RPM of about a 1000. I dont know about your other problems.