Very long exposure

Hello!

My name is Erin, I am from south africa and I am currently studying at UCT.
I am trying to make a camera that can take a photo over a few days indoors and I am struggling to get it right, would love some help! not sure which forum to put this in.
I have been using a pinhole camera, standard photographic pape rand a diy nd filter (welding glass) but I haven't had much success.

I leave the cameras in my studio for a few days.
this is a 12 hour exposure
these are 24 hour exposures

Paper negatives can come close to that multi-day exposure -- you've got good exposure on the 24-hour, which I presume was paper negatives, even though there's a window and exterior visible through it. If you avoid the windows, you'd probably be fine with the same combination for two or even four days.

Beyond that, go bigger. Larger cameras tend to have slower pinholes -- I have a couple that are in the f/295 range, vs. the f/128 range for my smaller ones. A couple stops, plus reciprocity breakdown, can push a 24-hour exposure out to multiple days.