Project freezes every time I klick at the Timeline

I did some work in a ongoing project earlier in the day and everything seemed to work fine. Next time I tried to open the project and klicked where in the timeline I wanted to work, a black square appeared and the program froze. I could find no way to affect it other than to force quit.

I suspect that I have to many layers in one timeline but I don’t know how to move some of the layers to another project ore timeline when I can’t enter the project without it shutting down. I dread having to redo everything. Please help!