Just for you to know, there is no overall project size limit. However, there is a 5 MB JSON limit and no asset can exceed 10 MB.
It is there so that projects don't take up too much server space.

I've had projects that take up to much space crash my chromebook That's probably another reason.

There might not be a 10MB file size limit for the entire Scratch project. (Unless you're talking about asset file sizes.)
Sometimes Scratch just really dislikes a specific song and won't let you load with it. It's infuriating, but if you're really attached to the song (like I was when it happened), there is a tedious solution.
The solution I found is to remove the sound from the original project so it saves, and open like 20 new projects, each of them an attempt to put the song in the project. When it finally works, delete all failed sound loading projects and build around the one with the song in it to become your previous project (like maybe backpacking sprites).
The problem might not be sound, and if it isn't, then ignore this reply.

Hey guys! Thanks for your answers! But i'm not really interested in this topic anymore, so i'm closing it. Scratch on!