If you're not clear on what someone says, ask.
I thought you wanted to fix\troubleshoot your problem, not worry about my lack of tact when attempting to help.
DTC has already been expanded on.
VCDS is what most of us who wrench on some of the lemons we drive is the diagnostic tool most commonly used.
Very powerful, and it's crucial in giving you insight to what you're dealing with.... and a good value.
There are training docs readily available if you know what to search for that will give you info on the other acronyms that we are throwing around. I have no idea of you level of aptitude, but when someone rips into a slushbox to replace solenoids, some of us assume some things. My bad!
When you want help, tell us as many details as possible. Engine and transmission codes, the fact that this is your first car and that you're a dentist who's always wanted to fix a heap, or whatever else we need to know.... we can't always read between the lines or guess correctly..... this is why people get all sideways because I'm a jack@$$.
So.... some reading that might help you ask the next question, if you choose to do so
If you are still wanting to go deeper into things, you need to start looking at service manuals. Sometimes those can be found with a bit of searching, or the easiest way is to purchase the exact documents that you're after from a place like Alldata, erWin, etc.
Anywhoo....... that should tie you up for a little or hit another nerve, or whatever. I tried.