Diagnosis Please

Hey, need some help trying to figure out a problem with a few photos. For context, I recently bought a new 135mm lens for my Olympus om1 off the internet - it was very cheap and gets jammed if I lower the aperture below f8.0 (but this isn’t the issue I want help with)…

I recently took my camera and 3 rolls to India for a trip with friends, the rolls did pass through the scanners on multiple occasions due to airport security not allowing me to pass it around. This trip was the first time trying out the lens and I have had mixed results.

Pictures 1 and 4 were shot on the same day - similar lighting conditions on the same film, the only difference being that 4 was shot on my 50mm lens.

Number 2 - there is a blur to the whole image - I suspect I wasn’t using a high enough shutter speed?

Number 3 - why is there so much grain to the image, also similar to 1 the colours all seem quite faded.

5/6 - both turned out okay in my opinion, my guess is brighter day so I was able to push the shutter speed higher?

Any thoughts would be greatly appreciated, as I’m not sure whether I just ditch the lens as to avoid wasting those precious (expensive) shots.