1. Loose weight
2. Get fitter, more long rides
3. Interval sessions
4.Increase leg strength at gym using weights
5. Turbo interval sessions in very high gear, not spin
6. Do not stand and climb as you lose rear wheel traction on MTB so practice climbing sat on the seat
There’s nothing special about hills its a combination of power to weight ratio. Less weight more power is what you want.
Technique can help, the lowest gear isnt always the best for climbing. Spinning like a nutter just increases hear rate. Try slightly higher gear keeps hear rate lower. On techy climbs you need to blast up or get over obstacle a higher gear can help to.
Points one and two are key 😉