QGIS 3.6.1 problems with CRS

Question

After I have created a new QGIS project, the project CRS is set automatically to WGS84 (EPSG:4326 - WGS 84 - Geographic). The layer (.shp) which I loaded to the project has already a predefined CRS (also WGS84). I want to change the CRS to a projected CRS to make some calculations so I set the appropriate CRS both for the layer and for the project (EPSG:32632 - WGS 84 / UTM zone 32N – Projected). In the project properties (General Tab) WGS84 is set as the ellipsoid for distance and area calculations.

Although both the project and the layer(s) have exactly the same CRS, the layer is displayed in a geographical CRS (WGS84):

Changing the layer CRS back to WGS84 I actually get the correct display (as a projected CRS - UTM32N) although the layer CRS is wrong (WGS84):

To check the correct position I also loaded OSM as basemap. Using WGS84 I get the following result (exptected for UTM...):

project: WGS84

layer: WGS84

OSM basemap: WGS84

ellipsoid: WGS84

while by:

project: UTM32N

layer: UTM32N

OSM basemap: UTM32N

ellipsoid: WGS84 or GRS80

I am landing in the western coast of Middle Africa.

This is really annoying. Do I misunderstand anything generally regarding CRS settings in QGIS or what is the problem?

Answer 1

Following on Ian Turton's comment... Prior to performing ANY geometry calculations or analysis on a layer(s), the layer(s) MUST be 1) projected to the desired CRS, and 2) that CRS must be the same for all layers. (Sidenote #1: in QGIS, projecting a layer to a different CRS is typically accomplished using Save As...)

Your analysis will always fail if the above conditions are not met. Setting the project CRS only affects how the layers are screen displayed; any geometric calulations or analysis will be conducted on the layer(s) source CRS, NOT the project's CRS. (Sidenote #2: Geometric calculations or analysis are usually done with CRS values in feet or meters, not lat/long.

These requirements are software-agnostic.