[adrusi]

while at the same time being memory safe.

memory safety doesn't mean just one thing, but probably it requires either a lot of rust-like features, a tracing garbage collector, or automatic reference counting.

the language being small enough that all basics can be grasped in a day

that disqualifies taking the rust-like path.

able to use all c libraries through ffi. without loss of performance or extra fu.

that disqualifies most (all?) advanced tracing gc strategies

it must not have massive pauses or stop the world GC.

that disqualifies simpler tracing gc strategies

depending on what precisely you're looking for, it's possible it might be a pipe dream. but it's also possible you'll find what you want in one of D, Nim or Swift. Swift is probably the closest to what you want on technical merit, but obviously extremely tied to Apple. D and Nim strap you with their particular flavor of tracing gc, which may or may not be suited to your needs.