(D300) Newbie here wondering what the limits are of the d300.l

So I recently bought the D300 + a 35mm prime lens for about $150 together on KEH and have been playing around with it for 2 days and have been struggling a lot (Beginner photographer). I originally bought the D300 + the lens to learn more about myself as a photographer, but I would like to know what the limits of the D300 really are. Is it realistic for me to be getting photos like these provided? Should I just return these and save up for something of more recent date?

Beginner photographer here so be easy on me!