Your question is quiet broadly scoped, but I will try to fill in some of your questions.
Regarding ‘our’ API’s/LinkedData/Sparql endpoints, the ‘only’ information we have on our website
If it is lacking, we would love to hear what you think is missing (or where we can improve upon)
Maybe you can elaborate a bit, so we (or others) have a bit more focus. For example: does it involve front-end/back-end systems is it ETL related (import/export data), maybe INSPIRE/European validation, and so on…
We did do some courses/workshop in the past,… We do have some use-case and demonstrators, you can find them here for LinkeData/Sparql and for OGC services/api a workshop
So that would be my suggestions, for now…