I'm 17 years old and i weigh 67 kg, i have been working out at the gym for 3 months now and i was wondering if its safe for me to take creatine monohydrate for muscle gain and how much should i take a day?

Taking creatine will not do you any good, other than lightening your wallet. If you are eating a mixed diet, you do not need any supplements. For healthy diet: http://www.choosemyplate.gov/., exercise 30 minutes/day, drink enough water daily so your urine is mostly colorless, have safe sex, no tobacco alcohol weed or street drugs. Get HPV and Covid vaccines. Wish you good health!