How long does it take for a torn tendon to heal? Is there anything I can do to speed up the healing process?
How do you know it's torn? This is doctor stuff, anything here is speculation especially without details. Generally shoulder problems take a while, unless it's aggrevation of tendons/ligaments that can be dealt with using cortisone.
And of course after the healing's over the message is take added measures and precautions to avoid a repeat of whatever created the trauma. Alter the exercises, increase warmup, lower weight and increase reps, etc.