I've added some points from a CSV file by their coordinates using the WGS84. It fits perfectly with the shapefile i'm using as a basemap (Sirgas 2000). However, when I try to create a buffer zone around the points (to later intersect with the original shapefile), if I use the WGS projection it occupies all the screen and if I use the Sirgas 2000 it appears as a single circle in what I think to be a random place.
I've been doing this for quite a while on ArcMap, but I didn't have the need to use different coordinate systems. Perhaps I'm just missing something. Can someone bring a light into my problem?