Importing data into a project with a custom CRS incorrectly projected

How do I change the default CRS in Qgis?

To define the default Coordinate Reference System (CRS) used for new QGIS Projects, choose Settings > Options > on the CRS Tab > and the CRS for Projects section you can choose the Default Projection used when a new Project is created.
 

How to define a Custom CRS in QGIS?

Steps to Add Custom CRS projection in QGIS

1. 1.) Open up QGIS.
2. 2.) In the window, click on + or plus sign and give a name to the CRS.
3. 3.) Now after adding the custom projection or custom CRS, you can find the option to change the CRS of the layer or file added.

What is the purpose of on the fly CRS transformation in QGIS?

On The Fly (OTF) CRS Transformation



QGIS supports “on the fly” CRS transformation for both raster and vector data. This means that regardless of the underlying CRS of particular map layers in your project, they will always be automatically transformed into the common CRS defined for your project.