I reckon it should take you about a year. maybe less if you practice alot, or more if you never practice. But if you can read music, try looking at grades above grade 1. And make sure you always start your practise by doing some kind of starter like scales, arpeggios, that kind of thing. For Grade 1, everything is in C, G or F major, if I remember rightly, so try playing scales through those keys, maybe progressing to D major or Bb major when you get more comfortable. You could also look at the relative minor keys of these keys. Which is where you count down 3 keys. so for C-major, it is A-minor. D-minor for F mjor, and Eminor for Gmajor. These should help you. The key is to PRACTICE!! So keep oing with it, learn as much as possible, and you'll be fine. Once you have got your grade 1, everything else past it seems alot easier, it's just the basics of fingering and remembering that will make it hard. Try to do about an hour every few days. Hope this is some help!!