Hi Notalent,
congratulations to the VIVITAR. It is a very sharp and fast lens ... very nice to have.
This is mine with the Polish M42-adapter in the foreground. As I told you, it is optically wonderful (even at full aperture). Those who like to work manually will like it a lot. (...though automatic exposure in (A) mode perfectly works with all SIGMAs).
Here another low budget / high image quality recommendation:
REVUENON: 135mm / F:2.8
Your pictures:
Nicely done ... I like pic 2 best! Just one thing:
Watch your colours. your white balance does not really hit the nail!
Compare:
Colours should be balanced from too much yellow to more blue ... for my taste. Skin tones in particular say "thank you".
Go on shooting!!
See you with nice (and affordable!) pictures
Klaus