Transmission light, rough idle, and codes

[BoJeRo]

I have a 2001 X5 3.0. Just bought it 2months ago.
Last Sunday it started an erratic idle when started.
When in reverse there was quite a lag and then jerked the car back.
Transmission light came on and appeared to not engage first gear.
Has died upon starting about 4 times.

Codes read thus far:
First gear ratio
misfires on #1,2,3.
Throttle Valve Control Circuit.

About a month ago it had a o2 code which we cleared and did not reappear on the last reads.
Although the check engine light did come back on shortly after.
Had a mechanic friend read codes this week and then we got a Peake reader.
Planning on changing the tranny fluid & filter next week when the parts come in.
Trying to gather as much info before taking it in to an independent mechanic.
Any thoughts or experience?
Thanks in advance!
Jennifer