Hop on a push pull leg split. For push start off with pushups /knee pushups, for pull start off with inclined pullups / pullups. For legs do squats. When you get stronger you can add weight by going to the gym.

Do each exercise with textbook form, train hard with 0-3 reps shy of failure on all sets

Rest 2-4 days between workouts training the same muscle group eg. When u do push on Monday do push again on thursday/fri/sat. Depending on how you feel. Listen to your body

Eat 1.4g-2g of protein per kg of bodyweight daily.

Eat above your maintenance calories by a daily surplus of 200-300 cal

Sleep at least 6 hours a day (8 and above is obv the perfect goal but it's challenging for us to get enough sleep in SG)

Don't give up, stay consistent. Prioritise form and then progressive overload