Add punctuation: The dumbbell bar made of quality steel is about 51 cm long and has 17 cm of dumbbell surfaces
A: The dumbbell bar made of quality steel is about 51 cm long and has 17 cm of dumbbell surfaces.

Add punctuation: Internal battery Powers the device sensors for 38 hours depending on sensors
A: Internal battery: Powers the device + sensors for 38 hours (depending on sensors)

Add punctuation: Death September 28 1986 in Kolding Denmark
A:
Death: September 28, 1986 in Kolding, Denmark