I got hurt very badly lifting under the supervision of a so called "personal trainer". The bar for getting certified must be extremely low. He told me to go until failure, and to always do more reps than I thought I could.
One horrible SLAP tear, thousands of dollars in medical bills, and three years later, I can comfortably say that I will never lift above body weight ever again in my life.
Stay away from heavy weights unless you're working with a real professional - skip the personal trainer, and honestly, skip heavy weights unless you're a professional yourself. It is completely unnecessary - you can look great without benching four times your body weight.
The risk is not worth the reward. Don't be fooled by the cult-like communities online that are obsessed with dangerous and unnecessary exercise regimes.
The amount of injuries we see in clinic that are related to weight lifting is astonishing. Anecdotally, from an orthopedic standpoint, there is an outsized risk associated with weight lifting over all other sports. None of the injuries we see from other sports (outside of maybe American football) are as frequent or as severe as weight lifting ones.