I needed to load a shape in GRASS GIS to use the v.clean.snap function. The .shp was first viewed in QGIS, projected in 3857 or 4326, I don't remeber. After the adjustments in GRASS GIS I exported to shape. Now when I load the corrected version of my shape in QGIS my features are not in europe but in afrika and whatever CRS I pick it is never right. Did I mess up my file in GRASS? How can I correct that?
Overall GRASS is very particular about CRS definitions. It makes no difference how the data was viewed/projected in QGIS. What is important is the original CRS of the shapefile itself. This is included in the *.prj file that should be available along the the *.shp, *.shx and *.dbf.
If the *.prj is there, then you should create a new GRASS Location that exactly matches the CRS of that shapefile (as defined in the *.prj), then import into GRASS, do your processing and export back to a new shapefile.
If the *.prj is not there, then you need to check with the data provider to get the actual projection information.