Troubles callibrating; Round shapes come out wrong (pictures attached)

[avagoyamug 0]

Hey there,

I have recently bought and assembled my first printer, a 2013 Ultimaker Original (DIY) from someone who had it laying around unassembled.

I'm still having some issues though with my prints, first one:

Round shapes, like the eyes, or chin here, come out with a sharp angle/ridge. Any ideas what this could be?

Another thing is:

See how the outer 2 perimeters on both objects here also have this kind of "ridge" with a gap to the inner perimeters, which come out round.

Thanks for any advice on how to fix this!

[avagoyamug 0]

Another thing, I forgot to ask:

Yesterday, printing the "Babygroot" above, the printer just stopped printing half into the print without any error message inside Cura. Both fans kept running, but all motors stopped suddenly.

Is there a kind of log file I can look into, or is there something else I can do to figure out why this happened?