Clean up everything thoroughly (I can see plenty of dust and a least one hair), then after that clean up again, and again, and again.

Diffuse your light. Diffuse your light. Diffuse your light! You can use tracing paper (several layers), white transluent plastic bags, bubble wrap roll, packaging foam (the translucent one), etc. Place it between your light source and the scene. Be cheap, recycle, don't buy costly diffuser screens. An old plastic bag can do wonders.

Bounce the diffused light with a reflector (oposite side of the scene). It can be a white sheet of paper, a polystyrene plate, mylar emergency blanket (crumpled), etc. And/or use a second diffused light source.

Don't go crazy with your aperture. Full open is seductive (so much bluuuuuuuuuuur)... But you'll have way less focus/optical problems if you close your aperture one or two stops (for example: for an optic at 1.8 full open I'll go f2.8 -> still plenty of blur, and a way better optical quality). Keep in mind your optic is at its absolute best on the middle of the aperture scale (typically between f8 and f5.6).

On photo hardware side... Old and cheap is good. The old Nikon flash (sb-24 sb-26) you bought for 15$ at the flea market does exactly the same thing than a new modern crap (200$) in full manual mode.