Equip a two-handed weapon and your best bow with an elemental arrow. First eat a meal that boost your attack +3 like 5 mighty bananas. Shoot the Lynel's face with your bow that will stun them. Use your two-handed weapon and keep hitting him. When the Lynel starts to recover use Urbosa's Fury that will stun it again. Once you have a Savage Lynel Crusher and a 5 shot Savage Lynel Bow they are easier