Greetings of the day.
As for your first question, duration of treatment cannot be judged just based on the picture provided, doctor needs to look at a lot many more things to give an estimate of the same.
A quicker way for aesthetic corrections, like minimal gap, shape correction etc., is getting veneers.
Next Steps
consult your preferred doctor and they will tell you about option that's more viable and suitable for you, in terms of results, duration, longevity.
Health Tips
Direct composite veneers are also a good option, but a temporary one. A nicely done composite veneer can give be thought of like a preview for your more permanent options like porcelain veneers. Be open to all the options and choose what suits your needs the best and assist your doctor in achieving the best results.