I have a task to be tackled of which I am not sure, wheter it is even possible. I need to classify single trees/clusters of trees in a forest automatically using sentinel-2 data. Supervised classification should be extremely trick in my opinion. I have some ground data, so that certain pixels are identified as a specific kind of tree in a point layer. Is there any way to get the automatic classification done? Especially when that scheme should not only work on a single image but on several images of the same area?
NASA offer an advanced webinar course https://arset.gsfc.nasa.gov/land/webinars/advanced-land-classification that uses the Semi-Automatic classification plugin in QGIS. It will take you through step by step with Landsat imagery. You can use the same steps for Sentinel imagery. The Semi-automatic classification plugin comes with the best user documentation I have seen for a QGIS plugin. It's well worth a look and the time to work out how to use it.