Hey, Since most work while trekking is done by your legs and heart, you need to keep these two at the prime of health before you join any mountaineer expedition. You would like to start at least 2 months prior to the start of your trip. Start by jogging/running on treadmill. You should increase your speed and stamina slowly so that you can cover 5 kms in 40-45 minutes. Additionally you should do moderate leg exercises, like squats, lunges, stair climbs, etc. Do these regularly and u should be ready to climb that mountain of your dreams 😊👍