Reproject your data:
load your text file with EPSG:4326 as CRS
Right click on that layer and choose "Export --> Save features as..."
Choose the CRS you want your data to be in (WGS 84 58S)
Save it (choose a file format you like)
Add this new file to your project
Just a wild guess, to me it looks similar to a Lambert azimuthal equal-area projection, rotated 80 degrees (I mean, looking from N80E toward N100W direction).
(Above: North Pole area by QGIS 3.8 on EPSG:102017 North_Pole_Lambert_Azimuthal_Equal_Area, rotating 80.0 degrees).
As @Vince already stated in comments, Web Mercator is not suitable for this.
Reproject your layers (Save as...) to a local metric one. Regarding epsg.io this could be UTM Zone 54N (EPSG:3095) for example.
First import the data in the CSV it's actually in. Once the data is imported, then you can reproject it into the desired CRS.
The coordinates in your CSV are in latitude and longitude. This means they're actually in a geographic coordinate system. The standard/most commonly used geographic CRS is EPSG:4326.
Here's how your workflow should go (with the same ...