What exercises are safe for obese people. I want to loose weight seriously, I am 5.5ft at 250lbs. 33yrs old male.?

Walking! As a start, walking is great. Walking 30 min 5 times per week has been shown to improve health, including delaying diabetes, improving cholesterol, and lowering bp. For most people it feels manageable and is less intimidating than a gym. If you can't do that much, just start with what you can do each day, and work toward that goal.
Water aerobics. You are about 100 pounds overweight. Must reduce calorie intake, exercise daily, ear healthy. At your weight, the chance for long term success is only 1-2%. You might consider weight loss surgery. Best exercise to lose fat is slow exercise, frequently.