even though my pc can easily handle rage, rage suddenly wont autosave anymore (did it for the first 3 hours) saying there is no more space and I should lower my graphics

a) my pc HAS space

I am on the lowest graphics

how can I solve this problem?

You cannot have more than ~16 save games at the same time in the list, so you need to override one of them at some point (if I got you right).

I only have two that I keep overriding.